function [Continuity]=Continuityspline(M,it,norm,log,contourscale, zlims)
%ForceBalance Show the radial force balance
%   Plot the three radial forces for the given time-step it or averaged
%   over the range of time steps defined in it

if it==':'
    it=floor(0.95*size(M.t2d)):size(M.t2d);
end
switch nargin
    case 2
        contourscale=0.6;
        norm=false;
        log=false;
        zlims=[-inf inf];
    case 3
        log=false;
        contourscale=0.6;
        zlims=[-inf inf];
    case 4
        contourscale=0.6;
        zlims=[-inf inf];
    case 5
        zlims=[-inf inf];
    case 6
        
    otherwise
        error("Invalid number of arguments")
end

contourcolor=[0 0 0];%[255 20 147]/255;

N=M.N(:,:,it);
densitycontour=contour(M.zgrid,M.rgrid,mean(N,3),[contourscale contourscale]*maxdens);
rgridmax=sum(M.nnr(1:2));

%% Continuity
f3=figure();
t=M.t2d(it);
dndt=zeros(size(N,1),size(N,2),size(N,3)-1);
ndivu=zeros(size(N,1),size(N,2),size(N,3)-1);
ugradn=zeros(size(N,1),size(N,2),size(N,3)-1);
parfor i=1:size(N,3)-1
    dndt(:,:,i)=(N(:,:,i+1)-N(:,:,i))./(t(i+1)-t(i));
    
    ndivu(:,:,i)=N(:,:,i).*(M.fluidUR.der(:,:,it(i),[1 0])...
        + M.fluidUR(:,:,it(i)).*Rinv...
        + M.fluidUZ.der(:,:,it(i),[0 1]));
    
   ugradn(:,:,i)=  M.fluidUR(:,:,it(i)).*M.N.der(:,:,it(i),[1 0]) ...
        + M.fluidUZ(:,:,it(i)).*M.N.der(:,:,it(i),[0 1]);
end
Continuity.dndt=dndt;
Continuity.ndivu=ndivu;
Continuity.ugradn=ugradn;


ax7=subplot(4,1,1);
plotvalue(ax7,mean(Continuity.dndt,3),'\partialn/\partialt','\partialn/\partialt [m^{-3}s^{-1}]',true)


zlim=[max([min(min(mean(Continuity.ndivu(2:end,:,:),3))),min(min(mean(Continuity.ugradn(2:end,:,:),3)))]) min([max(max(mean(Continuity.ndivu(2:end,:,:),3))),max(max(mean(Continuity.ugradn(2:end,:,:),3)))])];

ax8=subplot(4,1,2);
plotvalue(ax8,mean(Continuity.ndivu,3),'n\nabla(u)','n\nabla(u)[m^{-3}s^{-1}]',true,zlim)

ax9=subplot(4,1,3);
plotvalue(ax9,mean(Continuity.ugradn,3),'u\nabla(n)','u\nabla(n)[m^{-3}s^{-1}]',true,zlim)

ax10=subplot(4,1,4);
plotvalue(ax10,mean(Continuity.ndivu+Continuity.ugradn+Continuity.dndt,3),'Total','total[m^{-3}s^{-1}]',true,zlim)

sgtitle(sprintf('Continuity t=[%1.2g-%1.2g]s n_e=%1.2g m^{-3}',M.t2d(min(it)),M.t2d(max(it)),double(maxdens)))
f3.PaperOrientation='portrait';
[~, name, ~] = fileparts(M.file);
f3.PaperUnits='centimeters';
papsize=[20 19];
f3.PaperSize=papsize;
print(f3,sprintf('%scontinuity',name),'-dpdf','-fillpage')


    function plotvalue(axis,matrix,titl, clab, rm1strow, zlims)
        if nargin < 5
            rm1strow=false;
        end
        if nargin>5
            zmin=zlims(1);
            zmax=zlims(2);
        else
            zmin=-inf;
            zmax=inf;
        end
        if rm1strow
            if log
                h=surface(axis,M.zgrid,M.rgrid(2:end),abs(matrix(2:end,:)));
            else
                h=surface(axis,M.zgrid,M.rgrid(2:end),matrix(2:end,:));
            end
        else
            if log
                h=surface(axis,M.zgrid,M.rgrid,abs(matrix));
            else
                h=surface(axis,M.zgrid,M.rgrid,matrix);
            end
        end
        set(h,'edgecolor','none');
        hold on;
        if log
            zpos=interp2(M.zgrid, M.rgrid, abs(matrix), densitycontour(1,2:end), densitycontour(2,2:end));
        else
            zpos=interp2(M.zgrid, M.rgrid, matrix, densitycontour(1,2:end), densitycontour(2,2:end));
        end
        plot3(axis,densitycontour(1,2:end),densitycontour(2,2:end),zpos,'-.','linewidth',2,'color',contourcolor)
        xlabel(axis,'z [m]')
        ylabel(axis,'r [m]')
        xlim(axis,[M.zgrid(1) M.zgrid(end)])
        ylim(axis,[M.rgrid(1) M.rgrid(rgridmax)])
        colormap(axis,'jet')
        c = colorbar(axis);
        c.Label.String=clab;
        caxis(axis,[zmin zmax])
        if norm
            caxis(axis,[Fminr Fmaxr]);
        end
        if log
            set(axis,'colorscale','log')
        end
        title(axis,titl)
        grid(axis, 'on')
        view(axis,2)
    end
end