# Plot 2D streamline_issue

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MS on 9 May 2020
Commented: MS on 11 May 2020
I need a help to plot 2D streamline along with the contour plot. I am unable to plot the steamline properly(startx,stary). I am attaching my plot in the figure. It is starting from the middle for some reason. kindly help me to solve it. I am attaching the data files for your refernce to test it.
navg = 11;
filenames = cell(navg,1);
for i = 1:navg
filenames = sprintf('queen2_test_%d.txt', i);
mydata{i}=importdata(filenames);
% writematrix(avg_mat{i}, filenames{i});
R = mydata{i}(:,1);%X
C = mydata{i}(:,2);%Y
U = mydata{i}(:,3);
V = mydata{i}(:,4);
F = mydata{i}(:,7)./5;%F(X,Y)
F(isnan(F)) = 0;
% F = max(F,0);
rg = linspace(0, max(R), 100);
cg = linspace(0, max(C), 100);
[Rg, Cg] = meshgrid(rg, cg);
Fg = griddata(R, C, F, Rg, Cg);
Ug = griddata(R, C, U, Rg, Cg);
Vg = griddata(R, C, V, Rg, Cg);
figure
ax = axes();
caxis([-5 5])
colorbar
ax.YDir = 'reverse';
% ax.Position(2) = ax.Position(2)+0.02;
hold on;
[CC,HH] = (contourf(Rg,Cg,Fg));
set(HH,'LineColor','none')
% contourf(peaks(20),10,'edgecolor','none');
colormap(bluewhitered);
ax.XAxisLocation = 'top';
% cb = colorbar('Location', 'south');
% cb.Position(2) = cb.Position(2)-0.11;
grid on;
hold on
xstart = linspace(.025, max(R),300);
ystart = .005*ones(size(xstart));
s = streamline(Rg,Cg,Ug,Vg,Rg,Cg,[0.1,10000]);
% s = streamline(Rg,Cg,Ug,Vg,xstart,ystart,[0.1,10000]);
% [s.Color] = deal('g');
quiver(R,C,U,V);
end
Ameer Hamza on 9 May 2020
variable Ug and Vg are also not defined in this code. Can you give the code with generates the figure in question?

Ameer Hamza on 10 May 2020
Try this code
navg = 11;
filenames = cell(navg,1);
for i = 1:navg
filenames = sprintf('queen2_test_%d.txt', i);
mydata{i}=importdata(filenames);
R = mydata{i}(:,1);%X
C = mydata{i}(:,2);%Y
U = mydata{i}(:,3);
V = mydata{i}(:,4);
F = mydata{i}(:,7)./5;%F(X,Y)
rg = linspace(0, max(R), 100);
cg = linspace(0, max(C), 100);
[Rg, Cg] = meshgrid(rg, cg);
Fg = griddata(R, C, F, Rg, Cg);
Ug = griddata(R, C, U, Rg, Cg);
Vg = griddata(R, C, V, Rg, Cg);
figure
ax = axes();
caxis([-5 5])
colorbar
ax.YDir = 'reverse';
hold on;
contourf(Rg,Cg,Fg);
colormap(bluewhitered);
ax.XAxisLocation = 'top';
grid on;
hold on
quiver(R,C,U,V)
%%%%% streamline plot section start
xstart = linspace(0, max(R), 50);
ystart = 0.004*ones(size(xstart));
s = streamline(Rg,Cg,Ug,Vg,xstart,ystart);
%%%%% streamline plot section end
axis([0.02 0.07 .01 0.1])
set(gca,'XTick',0.02:.02:.07)
set(gca,'XTickLabel',0.2:0.2:.7)
set(gca,'YTick',0:.02:.1)
set(gca,'YTickLabel',0:0.2:1)
xlabel('x/c')
ylabel('y/c')
h = colorbar;
pos = get(h,'Position');
h.Label.Rotation = 0;% to rotate the text
h.Label.Interpreter = 'latex';
h.Label.String = '\$\ C_{p}\$';
set(gca, 'Color', 'black');
%saveas(gcf,filenames(1:end-4),'png');
exportgraphics(gcf,[filenames(1:end-4),'.png'], 'Resolution', 600);
delete(gcf);
end
MS on 10 May 2020
Thank you ameer. I am able to save the .fig files using the follwing command line as you suggested.
savefig([filenames(1:end-4),'.fig']);
I will update a command line if i am able to make any progress about the stream line.
MS on 11 May 2020
I tried to increase the numbers. Still, i get the same issue here.
xstart = linspace(0, max(R), 1000);
ystart = 0.005*ones(size(xstart));
s = streamline(Rg,Cg,Ug,Vg,xstart,ystart);
[s.Color] = deal('g');