# Plotting the content of huge matrix.

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Vira Roy on 29 Apr 2022
Commented: Vira Roy on 29 Apr 2022
Problem: I have a huge 449x10001 dimension matrix and want to make a scatter plot from that. While for loop works good enough for smaller size, plotting this huge matrix is extremely time and resource consuming. (I am aware this is a bad way of coding the problem, sorry)
I have attached a smaller version of the huge matrix here and shown my code below. This code here with matrix dimension 449x50 takes 31 seconds to do the plot. Is there a better way without using a for loop to access the entries and make the plot.
It would be extremely helpful if you can guide someway here. Thank you.
My code(attached are big_mat.mat and yaxis.mat)
x = linspace(1,449,449);
y_ = matfile('yaxis.mat');
spectral_wt = matfile('big_mat.mat');
S_wt = spectral_wt.spectral_wt;
y = y_.y;
for i = 1 : 50
scatter(x,y(:,i),[],S_wt(:,i),'filled')
hold on
colormap default
colorbar
ylabel('Energy')
xticks([0 64 128 192 256 320 384 448])
xticklabels({'\Gamma','M1','M2','M3','X1','X2','X3','R'})
xline([64,128,192,256,320,384,448]);
end

KSSV on 29 Apr 2022
Edited: KSSV on 29 Apr 2022
You need not to use scatter in a loop. You can do all this at one go using scatter or you can use pcolor as shown below.
x = linspace(1,449,449);
y_ = matfile('yaxis.mat');
spectral_wt = matfile('big_mat.mat');
S_wt = spectral_wt.spectral_wt;
y = y_.y;
X = repmat(x,size(y,2),1)' ;
Y = y ;
Z = S_wt ;
pcolor(X,Y,Z)
colormap default
colorbar
ylabel('Energy')
xticks([0 64 128 192 256 320 384 448])
xticklabels({'\Gamma','M1','M2','M3','X1','X2','X3','R'})
xline([64,128,192,256,320,384,448]);
Vira Roy on 29 Apr 2022
Thanks a ton. Really. Thank you so much.

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