how to create different matrices?

i have 30,000 rand value that i want to separate 400 to 400...then i wanna plot them but the x axis should start at 0 not 400 or 800 or...any help please?

[DGM]

What does "i want to separate 400 to 400" mean?

"x axis should start at 0 not 400 or 800 or..."

It would be clearer to say what both xlimits are. Are they [0 29999]? Are they [0 399]? Maybe [1 400]?

[arian hoseini]

yes sorry i meant i need the first 400 num of that matrix(30000) to be plot start from 1 to 400 next one should be 401 to 800 then...and i need to save these plot with saveas(gcf,[num2str(i),'.jpg']) and i need the first 400 num in a matrix then next one in another matrix...

[arian hoseini]

for the matrix lets say i have 10 num in a matrix but i want to change it into 10 matrices...

[1 2 3 4 5 6 7 8 9 10]

[1]

[2]

.

.

[10]

Answer 1

[Jonas]

you could split them into multiple 400x1 vectors by this

data=rand(30000,1);
data=reshape(data,400,1,[]);
size(data)

ans = 1×3

400 1 75

you can then get each vector using indexing data(:,:,idx)

for idx=1%:75 % commented out to avoid to much plotting here
    plot(0:399,data(:,:,idx));
    % saveas(gcf,[num2str(idx),'.jpg']);
end

[arian hoseini]

thank u sir it helped me alot but about the plot i want next plot to start from 401 and the next one start from 801 and....

[Stephen23]

"...but about the plot i want next plot to start from 401 and the next one start from 801 and...."

That is what Jonas' code does.

[DGM]

Are you saying that you want 75 individual plots? What are you going to do with them all?

[arian hoseini]

no every figure shows 0 to 400

[arian hoseini]

yes DGM i need 75 individual plots i wanna use them in ANN

[DGM]

0:400 is 401 elements, not 400. If x is supposed to correspond to integer-valued indices of the data, then it's going to be 1:400 or 0:399

Also, how would you feed a figure to an NN? As an image? Why is plotting even necessary at all?

[arian hoseini]

as an image and plot is not necessary but i wanna make sure that im doing it correctly ....i do it with python...just help me how to have 75 plot...jonas helped alot but the problem is every figure start at 0 to 399 i need them to be continued like second plot be 400 to 799 and....

[Jonas]

just change

 plot(0:399,data(:,:,idx));

to

 plot((0:399)+(idx-1)*400,data(:,:,idx));

[arian hoseini]

thank u sir...i learned so much...

[DGM]

You can do that, but you'll have to figure out how you want the image shaped, whether you want the ticks plotted, etc.

npoints = 30000; % or some multiple of 400
blocklen = 400;
startidx = 0;

% generate x,y
x = startidx:startidx+npoints-1;
y = rand(npoints,1);

% reshape
x = reshape(x,blocklen,[]);
y = reshape(y,blocklen,[]);

% plot and capture
nframes = size(x,2);
allframes = cell(nframes,1);
for k = 1:nframes
    plot(x(:,k),y(:,k))
    allframes{k} = frame2im(getframe(gcf));
end

This will save all the frames in a cell array. Alternatively, you can write them using imwrite().

Note that as images, the details of the start/end indices is moot, since the ticks aren't going to show that detail well enough for anyone to tell. You could always try to enforce the exact axis limits, but it's still not going to help much.

% place this in the loop between plotting and capture
xlim(x([1 end],k))
ylim([0 1])

[arian hoseini]

thanks