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Ch8_lib.py
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rJNAL Jupyter notebooks for Linear Algebra
Ch8_lib.py
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import
sys
,
os
sys
.
path
.
append
(
'../Librairie'
)
import
AL_Fct
as
al
import
numpy
as
np
import
sympy
as
sp
from
IPython.utils
import
io
from
IPython.display
import
display
,
Latex
,
Markdown
import
plotly
import
plotly.graph_objects
as
go
def
vector_plot_3D
(
v
,
b
):
"""
Show 3D plot of a vector (v) and of b = A * v
@param v: numpy array of shape (3,)
@param b: numpy array of shape (3,)
@return:
"""
fig
=
go
.
Figure
()
fig
.
add_trace
(
go
.
Scatter3d
(
x
=
[
0
,
v
[
0
]],
y
=
[
0
,
v
[
1
]],
z
=
[
0
,
v
[
2
]],
line
=
dict
(
color
=
'red'
,
width
=
4
),
mode
=
'lines+markers'
,
name
=
'$v$'
))
fig
.
add_trace
(
go
.
Scatter3d
(
x
=
[
0
,
b
[
0
]],
y
=
[
0
,
b
[
1
]],
z
=
[
0
,
b
[
2
]],
line
=
dict
(
color
=
'royalblue'
,
width
=
4
,
dash
=
'dash'
),
mode
=
'lines+markers'
,
name
=
'$A \ v$'
))
fig
.
show
()
def
CheckEigenVector
(
A
,
v
):
"""
Check if v is an eigenvector of A, display step by step solution
@param A: square sympy Matrix of shape (n,n)
@param v: 1D sympy Matrix of shape (n,1)
@return:
"""
# Check Dimensions
if
A
.
shape
[
0
]
!=
A
.
shape
[
1
]
or
v
.
shape
[
0
]
!=
A
.
shape
[
1
]:
raise
ValueError
(
'Dimension problem, A should be square (n x n) and v (n x 1)'
)
if
v
==
sp
.
zeros
(
v
.
shape
[
0
],
1
):
display
(
Latex
(
"$v$ est le vecteur nul, il ne peut pas être un vecteur propre par définition."
))
else
:
# Matrix Multiplication
b
=
A
*
v
# Print some explanation about the method
display
(
Latex
(
"On voit que $ b = A v = "
+
latexp
(
b
)
+
"$"
))
display
(
Latex
(
"On cherche alors un nombre $\lambda \in \mathbb{R}$ tel que $b = \lambda v"
\
+
"\Leftrightarrow"
+
latexp
(
b
)
+
" = \lambda"
+
latexp
(
v
)
+
'$'
))
# Symbol for lambda
l
=
sp
.
symbols
(
'\lambda'
,
real
=
True
)
# Check if there is a solution lambda of eq: A*v = lambda * v
eq
=
sp
.
Eq
(
b
,
l
*
v
)
sol
=
sp
.
solve
(
eq
,
l
)
# If there is l st b = l*v
if
sol
:
display
(
Latex
(
"Il existe bien une solution pour $\lambda$. Le vecteur $v$ est donc un vecteur
\
propre de la matrice $A$."
))
display
(
Latex
(
"La valeur propre associée est $\lambda = "
+
sp
.
latex
(
sol
[
l
])
+
"$."
))
# Otherwise
else
:
display
(
Latex
(
"L'equation $b = \lambda v$ n'a pas de solution."
))
display
(
Latex
(
"Le vecteur $v$ n'est donc pas un vecteur propre de la matrice $A$."
))
def
ch8_1_exo_2
(
A
,
l
,
vp
,
v
):
"""
Display step by step
@param A: Square sympy matrix
@param l: eigenvalue (float or int)
@param vp: Boolean, given answer to question is l an eigenvalue of A
@param v: proposed eigenvector
@return:
"""
# Check Dimensions
if
A
.
shape
[
0
]
!=
A
.
shape
[
1
]
or
v
.
shape
[
0
]
!=
A
.
shape
[
1
]:
raise
ValueError
(
'Dimension problem, A should be square (n x n) and v (n x 1)'
)
n
=
A
.
shape
[
0
]
eig
=
list
(
A
.
eigenvals
()
.
keys
())
for
i
,
w
in
enumerate
(
eig
):
eig
[
i
]
=
float
(
w
)
eig
=
np
.
array
(
eig
)
if
np
.
any
(
abs
(
l
-
eig
)
<
10
**-
10
):
if
vp
:
display
(
Latex
(
"$\lambda = "
+
str
(
l
)
+
"$ est bien une valeur propre de la matrice $A$."
))
else
:
display
(
Latex
(
"Non, $\lambda = "
+
str
(
l
)
+
"$ est bien une valeur propre de la matrice $A$."
))
if
v
!=
sp
.
zeros
(
n
,
1
):
# Check the eigen vector v
z
=
sp
.
simplify
(
A
*
v
-
l
*
v
)
if
z
==
sp
.
zeros
(
n
,
1
):
display
(
Latex
(
"$v$ est bien un vecteur propre de $A$ associé à $\lambda = "
+
str
(
l
)
+
"$ car on a:"
))
display
(
Latex
(
"$$"
+
latexp
(
A
)
+
latexp
(
v
)
+
"= "
+
str
(
l
)
+
"\cdot "
+
latexp
(
v
)
+
"$$"
))
else
:
display
(
Latex
(
"$v$ n'est pas un vecteur propre de $A$ associé à $\lambda = "
+
str
(
l
)
+
"$ car on a:"
))
display
(
Latex
(
"$$"
+
latexp
(
A
)
+
latexp
(
v
)
+
"
\\
neq \lambda"
+
latexp
(
v
)
+
"$$"
))
else
:
display
(
Latex
(
"$v$ est le vecteur nul et ne peut pas être par définition un vecteur propre."
))
else
:
if
vp
:
display
(
Latex
(
"En effet, $\lambda$ n'est pas une valeur propre de $A$."
))
else
:
display
(
Latex
(
"Non, $\lambda = "
+
str
(
l
)
+
"$ n'est pas une valeur propre de $A$."
))
def
red_matrix
(
A
,
i
,
j
):
""" Return reduced matrix (without row i and col j)"""
row
=
[
0
,
1
,
2
]
col
=
[
0
,
1
,
2
]
row
.
remove
(
i
-
1
)
col
.
remove
(
j
-
1
)
return
A
[
row
,
col
]
def
pl_mi
(
i
,
j
,
first
=
False
):
""" Return '+', '-' depending on row and col index"""
if
(
-
1
)
**
(
i
+
j
)
>
0
:
if
first
:
return
""
else
:
return
"+"
else
:
return
"-"
def
brackets
(
expr
):
"""Takes a sympy expression, determine if it needs parenthesis and returns a string containing latex of expr
with or without the parenthesis."""
expr_latex
=
sp
.
latex
(
expr
)
if
'+'
in
expr_latex
or
'-'
in
expr_latex
:
return
"("
+
expr_latex
+
")"
else
:
return
expr_latex
def
Determinant_3x3
(
A
,
step_by_step
=
True
,
row
=
True
,
n
=
1
):
"""
Step by step computation of the determinant of a 3x3 sympy matrix strating with given row/col number
@param A: 3 by 3 sympy matrix
@param step_by_step: Boolean, True: print step by step derivation of det, False: print only determinant
@param row: True to compute determinant from row n, False to compute determinant from col n
@param n: row or col number to compute the determinant from (int between 1 and 3)
@return: display step by step solution for
"""
if
A
.
shape
!=
(
3
,
3
):
raise
ValueError
(
'Dimension of matrix A should be 3x3. The input A must be a sp.Matrix of shape (3,3).'
)
if
n
<
1
or
n
>
3
or
not
isinstance
(
n
,
int
):
raise
ValueError
(
'n should be an integer between 1 and 3.'
)
# Construc string for determinant of matrix A
detA_s
=
sp
.
latex
(
A
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
# To print all the steps
if
step_by_step
:
# If we compute the determinant with row n
if
row
:
# Matrix with row i and col j removed (red_matrix(A, i, j))
A1
=
red_matrix
(
A
,
n
,
1
)
A2
=
red_matrix
(
A
,
n
,
2
)
A3
=
red_matrix
(
A
,
n
,
3
)
detA1_s
=
sp
.
latex
(
A1
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
detA2_s
=
sp
.
latex
(
A2
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
detA3_s
=
sp
.
latex
(
A3
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
line1
=
"$"
+
detA_s
+
' = '
+
pl_mi
(
n
,
1
,
True
)
+
brackets
(
A
[
n
-
1
,
0
])
+
detA1_s
+
pl_mi
(
n
,
2
)
+
\
brackets
(
A
[
n
-
1
,
1
])
+
detA2_s
+
pl_mi
(
n
,
3
)
+
brackets
(
A
[
n
-
1
,
2
])
+
detA3_s
+
'$'
line2
=
'$'
+
detA_s
+
' = '
+
pl_mi
(
n
,
1
,
True
)
+
brackets
(
A
[
n
-
1
,
0
])
+
"\cdot ("
+
sp
.
latex
(
sp
.
det
(
A1
))
\
+
")"
+
pl_mi
(
n
,
2
)
+
brackets
(
A
[
n
-
1
,
1
])
+
"\cdot ("
+
sp
.
latex
(
sp
.
det
(
A2
))
+
")"
+
\
pl_mi
(
n
,
3
)
+
brackets
(
A
[
n
-
1
,
2
])
+
"\cdot ("
+
sp
.
latex
(
sp
.
det
(
A3
))
+
')$'
line3
=
'$'
+
detA_s
+
' = '
+
sp
.
latex
(
sp
.
simplify
(
sp
.
det
(
A
)))
+
'$'
# If we compute the determinant with col n
else
:
# Matrix with row i and col j removed (red_matrix(A, i, j))
A1
=
red_matrix
(
A
,
1
,
n
)
A2
=
red_matrix
(
A
,
2
,
n
)
A3
=
red_matrix
(
A
,
3
,
n
)
detA1_s
=
sp
.
latex
(
A1
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
detA2_s
=
sp
.
latex
(
A2
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
detA3_s
=
sp
.
latex
(
A3
)
.
replace
(
'['
,
'|'
)
.
replace
(
']'
,
'|'
)
line1
=
"$"
+
detA_s
+
' = '
+
pl_mi
(
n
,
1
,
True
)
+
brackets
(
A
[
0
,
n
-
1
])
+
detA1_s
+
pl_mi
(
n
,
2
)
+
\
brackets
(
A
[
1
,
n
-
1
])
+
detA2_s
+
pl_mi
(
n
,
3
)
+
brackets
(
A
[
2
,
n
-
1
])
+
detA3_s
+
'$'
line2
=
'$'
+
detA_s
+
' = '
+
pl_mi
(
n
,
1
,
True
)
+
brackets
(
A
[
0
,
n
-
1
])
+
"\cdot ("
+
sp
.
latex
(
sp
.
det
(
A1
))
\
+
")"
+
pl_mi
(
n
,
2
)
+
brackets
(
A
[
1
,
n
-
1
])
+
"\cdot ("
+
sp
.
latex
(
sp
.
det
(
A2
))
+
")"
+
\
pl_mi
(
n
,
3
)
+
brackets
(
A
[
2
,
n
-
1
])
+
"\cdot ("
+
sp
.
latex
(
sp
.
det
(
A3
))
+
')$'
line3
=
'$'
+
detA_s
+
' = '
+
sp
.
latex
(
sp
.
simplify
(
sp
.
det
(
A
)))
+
'$'
# Display step by step computation of determinant
display
(
Latex
(
line1
))
display
(
Latex
(
line2
))
display
(
Latex
(
line3
))
# Only print the determinant without any step
else
:
display
(
Latex
(
"$"
+
detA_s
+
"="
+
sp
.
latex
(
sp
.
det
(
A
))
+
"$"
))
def
valeurs_propres
(
A
):
if
A
.
shape
[
0
]
!=
A
.
shape
[
1
]:
raise
ValueError
(
"A should be a square matrix"
)
l
=
sp
.
symbols
(
'\lambda'
)
n
=
A
.
shape
[
0
]
poly
=
sp
.
det
(
A
-
l
*
sp
.
eye
(
n
))
poly_exp
=
sp
.
expand
(
poly
)
poly_factor
=
sp
.
factor
(
poly
)
det_str
=
sp
.
latex
(
poly_exp
)
+
"="
+
sp
.
latex
(
poly_factor
)
display
(
Latex
(
"On cherche les valeurs propres de la matrice $ A="
+
latexp
(
A
)
+
"$."
))
display
(
Latex
(
"Le polynome caractéristique de $A$ est: $$\det(A- \lambda I)= "
+
det_str
+
"$$"
))
eq
=
sp
.
Eq
(
poly
,
0
)
sol
=
sp
.
solve
(
eq
,
l
)
if
len
(
sol
)
>
1
:
display
(
Latex
(
"Les racines du polynôme caractéristique sont $"
+
sp
.
latex
(
sol
)
+
"$."
))
display
(
Latex
(
"Ces racines sont les valeurs propres de la matrice $A$."
))
else
:
display
(
Latex
(
"L'unique racine du polynôme caractéristique est"
+
str
(
sol
[
0
])))
def
texVector
(
v
):
"""
Return latex string for vertical vector
Input: v, 1D np.array()
"""
n
=
v
.
shape
[
0
]
return
al
.
texMatrix
(
v
.
reshape
(
n
,
1
))
def
check_basis
(
sol
,
prop
):
"""
Checks if prop basis is equivalent to sol basis
@param sol: verified basis, 2D numpy array, first dim: vector indexes, second dim: idx of element in a basis vect
@param prop: proposed basis
@return: boolean
"""
prop
=
np
.
array
(
prop
,
dtype
=
np
.
float64
)
# number of vector in basis
n
=
len
(
sol
)
# Check dimension of proposed eigenspace
if
n
!=
len
(
prop
):
display
(
Latex
(
"Le nomber de vecteur(s) propre(s) donné(s) est incorrecte. "
+
"La dimension de l'espace propre est égale au nombre de variable(s) libre(s)."
))
return
False
else
:
# Check if the sol vector can be written as linear combination of prop vector
# Do least squares to solve overdetermined system and check if sol is exact
A
=
np
.
transpose
(
prop
)
lin_comb_ok
=
np
.
zeros
(
n
,
dtype
=
bool
)
for
i
in
range
(
n
):
x
,
_
,
_
,
_
=
np
.
linalg
.
lstsq
(
A
,
sol
[
i
],
rcond
=
None
)
res
=
np
.
sum
((
A
@
x
-
sol
[
i
])
**
2
)
lin_comb_ok
[
i
]
=
res
<
10
**
-
13
return
np
.
all
(
lin_comb_ok
)
def
eigen_basis
(
A
,
l
,
prop_basis
=
None
,
disp
=
True
,
return_
=
False
):
"""
Display step by step method for finding a basis of the eigenspace of A associated to eigenvalue l
Eventually check if the proposed basis is correct. Display or not
@param A: Square sympy Matrix with real coefficients
@param l: real eigen value of A (float or int)
@param prop_basis: Proposed basis: list of base vector (type list of list of floats)
@param disp: boolean if display the solution. If false it displays nothing
@param return_: boolean if return something or nothing
@return: basis: a correct basis for the eigen space (2D numpy array)
basic_idx: list with indices of basic variables of A - l*I
free_idx: list with indices of free variables of A - l*I
"""
if
not
A
.
is_Matrix
:
raise
ValueError
(
"A should be a sympy Matrix."
)
# Check if A is square
n
=
A
.
shape
[
0
]
if
n
!=
A
.
shape
[
1
]:
raise
ValueError
(
'A should be a square matrix.'
)
# Compute eigenvals in symbolic
eig
=
A
.
eigenvals
()
eig
=
list
(
eig
.
keys
())
# Deal with complex number (removal)
complex_to_rm
=
[]
for
idx
,
el
in
enumerate
(
eig
):
if
not
el
.
is_real
:
complex_to_rm
.
append
(
idx
)
for
index
in
sorted
(
complex_to_rm
,
reverse
=
True
):
del
eig
[
index
]
eig
=
np
.
array
(
eig
)
# evaluate symbolic expression
eig_eval
=
np
.
array
([
float
(
el
)
for
el
in
eig
])
# Check that entered eigenvalue is indeed an eig of A
if
np
.
all
(
abs
(
l
-
eig_eval
)
>
1e-10
)
and
len
(
eig
)
>
0
:
display
(
Latex
(
"$\lambda$ n'est pas une valeur propre de $A$."
))
return
None
,
None
,
None
# Change value of entered eig to symbolic expression (for nice print)
l
=
eig
[
np
.
argmin
(
np
.
abs
(
l
-
eig
))]
I
=
sp
.
eye
(
n
)
Mat
=
A
-
l
*
I
b
=
np
.
zeros
(
n
)
if
disp
:
display
(
Latex
(
"On a $ A = "
+
latexp
(
A
)
+
"$."
))
display
(
Latex
(
"On cherche une base de l'espace propre associé à $\lambda = "
+
str
(
l
)
+
"$."
))
# ER matrix
e_Mat
,
basic_idx
=
Mat
.
rref
()
# Idx of basic and free varialbe
basic_idx
=
list
(
basic_idx
)
basic_idx
.
sort
()
free_idx
=
[
idx
for
idx
in
range
(
n
)
if
idx
not
in
basic_idx
]
free_idx
.
sort
()
n_free
=
len
(
free_idx
)
# String to print free vars
free_str
=
""
for
i
in
range
(
n
):
if
i
in
free_idx
:
free_str
+=
"x_"
+
str
(
i
+
1
)
+
" \ "
# Display echelon matrix
if
disp
:
display
(
Latex
(
"On échelonne la matrice du système $A -\lambda I = 0 \Rightarrow "
+
al
.
texMatrix
(
np
.
array
(
Mat
),
np
.
reshape
(
b
,
(
n
,
1
)))
+
"$"
))
display
(
Latex
(
"On obtient: $"
+
al
.
texMatrix
(
np
.
array
(
e_Mat
[:,
:
n
]),
np
.
reshape
(
b
,
(
n
,
1
)))
+
"$"
))
display
(
Latex
(
"Variable(s) libre(s): $"
+
free_str
+
"$"
))
# Build a list of n_free basis vector:
# first dim: which eigenvector (size of n_free)
# second dim: which element of the eigenvector (size of n)
basis
=
np
.
zeros
((
n_free
,
n
))
for
i
in
range
(
n_free
):
basis
[
i
,
free_idx
[
i
]]
=
1.0
for
idx
,
j
in
enumerate
(
free_idx
):
for
i
in
basic_idx
:
basis
[
idx
,
i
]
=
-
float
(
e_Mat
[
i
,
j
])
# Show calculated basis
basis_str
=
""
for
idx
,
i
in
enumerate
(
free_idx
):
basis_str
+=
"x_"
+
str
(
i
+
1
)
+
" \cdot"
+
texVector
(
basis
[
idx
])
if
idx
<
n_free
-
1
:
basis_str
+=
" + "
if
disp
:
display
(
Latex
(
"On peut donc exprimer la base de l'espace propre comme: $"
+
basis_str
+
"$"
))
if
prop_basis
is
not
None
and
disp
:
correct_answer
=
check_basis
(
basis
,
prop_basis
)
if
correct_answer
:
display
(
Latex
(
"La base donnée est correcte car on peut retrouver la base calculée ci-dessus"
\
" avec une combinaison linéaire de la base donnée. "
"Aussi les deux bases ont bien le même nombre de vecteurs."
))
else
:
display
(
Latex
(
"La base donnée est incorrecte."
))
if
return_
:
return
basis
,
basic_idx
,
free_idx
def
generate_eigen_vector
(
basis
,
l
,
limit
):
"""
Function to generate a random eigenvector associated to a eigenvalue given a basis of the eigenspace
The returned eigenvector is such that itself and its multiplication with the matrix will stay in range of limit
in order to have a nice plot
@param basis: basis of eigenspace associated to eigenvalue lambda
@param l: eigenvalue
@param limit: limit of the plot: norm that the engenvector or its multiplication with the matrix will not exceed
@return: eigen vector (numpy array)
"""
n
=
len
(
basis
)
basis_mat
=
np
.
array
(
basis
)
.
T
basis_mat
=
basis_mat
.
astype
(
np
.
float64
)
coeff
=
2
*
np
.
random
.
rand
(
n
)
-
1
vect
=
basis_mat
@
coeff
if
abs
(
l
)
<=
1
:
vect
=
vect
/
np
.
linalg
.
norm
(
vect
)
*
(
limit
-
1
)
else
:
vect
=
vect
/
np
.
linalg
.
norm
(
vect
)
*
(
limit
-
1
)
/
l
return
vect
def
plot3x3_eigspace
(
A
,
xL
=-
10
,
xR
=
10
,
p
=
None
,
plot_vector
=
False
):
# To have integer numbers
if
p
is
None
:
p
=
xR
-
xL
+
1
n
=
A
.
shape
[
0
]
# Check 3 by 3
if
n
!=
3
or
n
!=
A
.
shape
[
1
]:
raise
ValueError
(
"A should be 3 by 3"
)
w
=
A
.
eigenvals
()
w
=
list
(
w
.
keys
())
# Deal with complex number (removal)
complex_to_rm
=
[]
for
idx
,
el
in
enumerate
(
w
):
if
not
el
.
is_real
:
complex_to_rm
.
append
(
idx
)
for
index
in
sorted
(
complex_to_rm
,
reverse
=
True
):
del
w
[
index
]
display
(
"Des valeurs propres sont complexes, on les ignore."
)
if
len
(
w
)
==
0
:
display
(
"Toute les valeurs propres sont complexes."
)
return
gr
=
'rgb(102,255,102)'
org
=
'rgb(255,117,26)'
# red = 'rgb(255,0,0)'
blue
=
'rgb(51, 214, 255)'
colors
=
[
blue
,
gr
,
org
]
s
=
np
.
linspace
(
xL
,
xR
,
p
)
t
=
np
.
linspace
(
xL
,
xR
,
p
)
tGrid
,
sGrid
=
np
.
meshgrid
(
s
,
t
)
data
=
[]
A_np
=
np
.
array
(
A
)
.
astype
(
np
.
float64
)
for
i
,
l
in
enumerate
(
w
):
l_eval
=
float
(
l
)
basis
,
basic_idx
,
free_idx
=
eigen_basis
(
A
,
l_eval
,
disp
=
False
,
return_
=
True
)
n_free
=
len
(
basis
)
if
n_free
!=
len
(
free_idx
):
raise
ValueError
(
"len(basis) and len(free_idx) should be equal."
)
gr
=
'rgb(102,255,102)'
colorscale
=
[[
0.0
,
colors
[
i
]],
[
0.1
,
colors
[
i
]],
[
0.2
,
colors
[
i
]],
[
0.3
,
colors
[
i
]],
[
0.4
,
colors
[
i
]],
[
0.5
,
colors
[
i
]],
[
0.6
,
colors
[
i
]],
[
0.7
,
colors
[
i
]],
[
0.8
,
colors
[
i
]],
[
0.9
,
colors
[
i
]],
[
1.0
,
colors
[
i
]]]
X
=
[
None
]
*
3
if
n_free
==
2
:
X
[
free_idx
[
0
]]
=
tGrid
X
[
free_idx
[
1
]]
=
sGrid
X
[
basic_idx
[
0
]]
=
tGrid
*
basis
[
0
][
basic_idx
[
0
]]
+
sGrid
*
basis
[
1
][
basic_idx
[
0
]]
plot_obj
=
go
.
Surface
(
x
=
X
[
0
],
y
=
X
[
1
],
z
=
X
[
2
],
showscale
=
False
,
showlegend
=
True
,
colorscale
=
colorscale
,
opacity
=
1
,
name
=
"$ \lambda= "
+
sp
.
latex
(
l
)
+
"$"
)
elif
n_free
==
1
:
plot_obj
=
go
.
Scatter3d
(
x
=
t
*
basis
[
0
][
0
],
y
=
t
*
basis
[
0
][
1
],
z
=
t
*
basis
[
0
][
2
],
line
=
dict
(
colorscale
=
colorscale
,
width
=
4
),
mode
=
'lines'
,
name
=
"$\lambda = "
+
sp
.
latex
(
l
)
+
"$"
)
elif
n_free
==
3
:
display
(
Latex
(
"La dimension de l'espace propre de l'unique valeur propre est 3: tous les vecteurs"
\
"$v \in \mathbb{R}^3 $ appartiennent à l'espace propre de la matrice $A$."
\
"On ne peut donc pas reprensenter sous la forme d'un plan ou d'une droite."
))
return
else
:
print
(
"error"
)
return
data
.
append
(
plot_obj
)
if
(
plot_vector
):
v1
=
generate_eigen_vector
(
basis
,
l_eval
,
xR
)
v2
=
A_np
@
v1
data
.
append
(
go
.
Scatter3d
(
x
=
[
0
,
v1
[
0
]],
y
=
[
0
,
v1
[
1
]],
z
=
[
0
,
v1
[
2
]],
line
=
dict
(
width
=
6
),
marker
=
dict
(
size
=
4
),
mode
=
'lines+markers'
,
name
=
'$v_{'
+
sp
.
latex
(
l
)
+
'}$'
))
data
.
append
(
go
.
Scatter3d
(
x
=
[
0
,
v2
[
0
]],
y
=
[
0
,
v2
[
1
]],
z
=
[
0
,
v2
[
2
]],
line
=
dict
(
width
=
6
,
dash
=
'dash'
),
marker
=
dict
(
size
=
4
),
mode
=
'lines+markers'
,
name
=
"$A \ v_{"
+
sp
.
latex
(
l
)
+
"}$"
))
layout
=
go
.
Layout
(
showlegend
=
True
,
# not there WHY???? --> LEGEND NOT YET IMPLEMENTED FOR SURFACE OBJECTS!!
legend
=
dict
(
orientation
=
"h"
),
autosize
=
True
,
width
=
800
,
height
=
800
,
scene
=
go
.
layout
.
Scene
(
xaxis
=
dict
(
gridcolor
=
'rgb(255, 255, 255)'
,
zerolinecolor
=
'rgb(255, 255, 255)'
,
showbackground
=
True
,
backgroundcolor
=
'rgb(230, 230,230)'
,
range
=
[
xL
,
xR
]
),
yaxis
=
dict
(
gridcolor
=
'rgb(255, 255, 255)'
,
zerolinecolor
=
'rgb(255, 255, 255)'
,
showbackground
=
True
,
backgroundcolor
=
'rgb(230, 230,230)'
,
range
=
[
xL
,
xR
]
),
zaxis
=
dict
(
gridcolor
=
'rgb(255, 255, 255)'
,
zerolinecolor
=
'rgb(255, 255, 255)'
,
showbackground
=
True
,
backgroundcolor
=
'rgb(230, 230,230)'
,
range
=
[
xL
,
xR
]
),
aspectmode
=
"cube"
,
)
)
fig
=
go
.
Figure
(
data
=
data
,
layout
=
layout
)
plotly
.
offline
.
iplot
(
fig
)
return
def
plot2x2_eigspace
(
A
,
xL
=
-
10
,
xR
=
10
,
p
=
None
):
if
p
is
None
:
p
=
xR
-
xL
+
1
w
=
A
.
eigenvals
()
w
=
list
(
w
.
keys
())
# Deal with complex number (removal)
complex_to_rm
=
[]
for
idx
,
el
in
enumerate
(
w
):
if
not
el
.
is_real
:
complex_to_rm
.
append
(
idx
)
for
index
in
sorted
(
complex_to_rm
,
reverse
=
True
):
del
w
[
index
]
display
(
"Une valeur propre est complexe, on l'ignore."
)
if
len
(
w
)
==
0
:
display
(
"Toute les valeurs propres sont complexes."
)
return
data
=
[]
for
i
,
l
in
enumerate
(
w
):
l_eval
=
float
(
l
)
basis
,
basic_idx
,
free_idx
=
eigen_basis
(
A
,
l_eval
,
disp
=
False
,
return_
=
True
)
n_free
=
len
(
basis
)
if
n_free
!=
len
(
free_idx
):
raise
ValueError
(
"len(basis) and len(free_idx) should be equal."
)
if
n_free
==
2
:
display
(
Latex
(
"Tous les vecteurs du plan appartiennent à l'espace propre de A associé à $\lambda = "
\
+
sp
.
latex
(
l
)
+
"$. On ne peut donc pas le représenter."
))
return
else
:
t
=
np
.
linspace
(
xL
,
xR
,
p
)
trace
=
go
.
Scatter
(
x
=
t
*
basis
[
0
][
0
],
y
=
t
*
basis
[
0
][
1
],
marker
=
dict
(
size
=
6
),
mode
=
'lines+markers'
,
name
=
"$\lambda = "
+
sp
.
latex
(
l
)
+
"$"
)
data
.
append
(
trace
)
layout
=
go
.
Layout
(
showlegend
=
True
,
autosize
=
True
)
fig
=
go
.
Figure
(
data
=
data
,
layout
=
layout
)
plotly
.
offline
.
iplot
(
fig
)
return
def
plot_eigspace
(
A
,
xL
=-
10
,
xR
=
10
,
p
=
None
):
"""
Plot the eigenspaces associated to all eigenvalues of A
@param A: Sympy matrix of shape (2,2) or (3,3)
@param xL: Left limit of plot
@param xR: Right limit of plot
@param p: Number of points to use
"""
n
=
A
.
shape
[
0
]
# Check 3 by 3 or 2 by 2
if
(
n
!=
2
and
n
!=
3
)
or
n
!=
A
.
shape
[
1
]:
raise
ValueError
(
"A should be 2 by 2 or 3 by 3."
)
if
not
A
.
is_Matrix
:
raise
ValueError
(
"A should be a sympy Matrix."
)
if
n
==
2
:
plot2x2_eigspace
(
A
,
xL
,
xR
,
p
)
else
:
plot3x3_eigspace
(
A
,
xL
,
xR
,
p
)
def
latexp
(
A
):
"""
Function to output latex expression of a sympy matrix but with round parenthesis
@param A: sympy matrix
@return: latex string
"""
return
sp
.
latex
(
A
,
mat_delim
=
'('
,
mat_str
=
'matrix'
)
def
ch8_8_ex_1
(
A
,
prop_answer
):
"""
Check if a matrix is diagonalisable.
@param A: sympy square matrix
@param prop_answer: boolean, answer given by the student
@return:
"""
if
not
A
.
is_Matrix
:
raise
ValueError
(
"A should be a sympy Matrix."
)
n
=
A
.
shape
[
0
]
if
n
!=
A
.
shape
[
1
]:
raise
ValueError
(
'A should be a square matrix.'
)
eig
=
A
.
eigenvects
()
dim_geom
=
0
for
x
in
eig
:
dim_geom
+=
len
(
x
[
2
])
answer
=
dim_geom
==
n
if
answer
:
display
(
Latex
(
"Oui la matrice $A = "
+
latexp
(
A
)
+
"$ est diagonalisable."
))
else
:
display
(
Latex
(
"Non la matrice $A = "
+
latexp
(
A
)
+
"$ n'est pas diagonalisable."
))
if
answer
==
prop_answer
:
display
(
Latex
(
"Votre réponse est correcte !"
))
else
:
display
(
Latex
(
"Votre réponse est incorrecte."
))
def
isDiagonalizable
(
A
):
"""
Step by step method to determine if a given matrix is diagonalizable. This methods uses always (I think)
the easiest way to determine it.
@param A: sympy matrix
@return: nothing
"""
if
not
A
.
is_Matrix
:
raise
ValueError
(
"A should be a sympy Matrix."
)
n
=
A
.
shape
[
0
]
if
n
!=
A
.
shape
[
1
]:
raise
ValueError
(
'A should be a square matrix.'
)
display
(
Latex
(
"On cherche à déterminer si la matrice $A="
+
latexp
(
A
)
+
"$ de taille $n
\\
times n$ avec $n = "
+
str
(
n
)
+
"$ est diagonalisable."
))
if
A
.
is_lower
or
A
.
is_upper
:
display
(
Latex
(
"Les valeurs propres sont simple à trouver, ce sont les éléments diagonaux."
))
else
:
valeurs_propres
(
A
)
# Check if eigenvalue are all distincts
eig
=
A
.
eigenvects
()
if
len
(
eig
)
==
n
:
display
(
Latex
(
"On a $n$ valeurs propres distinctes. La matrice est donc diagonalisable."
))
return
else
:
display
(
Latex
(
"Les valeurs propres ne sont pas toutes distinctes. On va donc vérifier la multiplicité "
+
"géométrique des valeurs propres ayant une multiplicité algébrique supérieur à 1."
))
# Some list to have info about eigenvalues with algebraic mult > 1
idx
=
[]
eigenvalues
=
[]
mult_al
=
[]
mult_geo
=
[]
for
i
in
range
(
len
(
eig
)):
if
eig
[
i
][
1
]
>
1
:
idx
.
append
(
i
)
eigenvalues
.
append
(
eig
[
i
][
0
])
mult_al
.
append
(
eig
[
i
][
1
])
mult_geo
.
append
(
len
(
eig
[
i
][
2
]))
display
(
Latex
(
"L'ensemble des valeurs propres ayant une multiplicité algébrique supérieur à 1 est "
+
str
(
eigenvalues
)
+
"."
))
for
i
,
l
in
enumerate
(
eigenvalues
):
display
(
Markdown
(
"**On calcule la multiplicité géométrique pour $\lambda= "
+
sp
.
latex
(
l
)
+
"$ ayant une multiplicité algébrique de "
+
str
(
mult_al
[
i
])
+
".**"
))
basis
,
basic
,
free
=
eigen_basis
(
A
,
l
,
prop_basis
=
None
,
disp
=
True
,
return_
=
True
)
display
(
Markdown
(
"**La multiplicité géométrique pour $\lambda= "
+
sp
.
latex
(
l
)
+
"$ est de "
+
str
(
len
(
free
))
+
".**"
))
if
(
len
(
free
)
<
mult_al
[
i
]):
display
(
Markdown
(
"**La multiplicité géométrique est strictement inférieur à la multiplicité"
"algébrique + pour cette valeur propre. La matrice n'est donc pas diagonalisable.**"
))
return
else
:
display
(
Latex
(
"On a bien multiplicité algébrique = multiplicité géométrique pour cette valeur propre."
))
display
(
Markdown
(
"**Toutes les valeurs propres ont une multiplicité algébrique et géométrique égales."
+
" La matrice $A$ est donc bien diagonalisable !**"
))
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