Mean of a Matrix

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BBB 2019-11-13

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评论： Adam 2019-11-13

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Hi,

I have a 51x51 2D matrix that I need to take a mean off, but it has to give me back a 51x51 2D matrix as an output.

Please see the sample code below:

rand_image_stim = rand(10000,51,51);
kk = 1:length(rand_image_stim);
firing_rate_kk(kk) = 0;
gab_filt = z_cos.*z_gauss;
lp(kk) = 0;
for kk = 1:length(rand_image_stim)
    output_kk = squeeze(rand_image_stim(kk,:,:)).*gab_filt;
    firing_rate_kk(kk) = sum(output_kk,'all');
    jk = squeeze(rand_image_stim(kk,:,:))*firing_rate_kk(kk);
    lp = mean(jk,2); %this is where I need help
end

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BBB 2019-11-13

How would I need to change my code then?

Thanks

Adam 2019-11-13

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I don't really have the time to look in depth at the code and give a full syntactically correct answer, but from what I can see you just want to store jk in the loop as e.g.

jk( kk, :, : ) = squeeze(rand_image_stim(kk,:,:))*firing_rate_kk(kk);

and remove the last line from the loop, then after the end of the for loop simply:

result = mean( jk );

should give what you want.

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Luna 2019-11-13

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编辑：Luna 2019-11-13

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your for loop is length(rand_image_stim). So your mean value calculated 10000 times. You should store it and later get the mean all.

Try this:

rand_image_stim = rand(10000,51,51);
kk = 1:length(rand_image_stim);
firing_rate_kk(kk) = 0;
gab_filt = z_cos.*z_gauss;
lp(kk,51) = 0; % 10000 x 51 matrix
for kk = 1:length(rand_image_stim)
    output_kk = squeeze(rand_image_stim(kk,:,:)).*gab_filt;
    firing_rate_kk(kk) = sum(output_kk,'all');
    jk = squeeze(rand_image_stim(kk,:,:))*firing_rate_kk(kk);
    lp(kk,:) = mean(jk,2); %this is where I need help
end
your_mean_value = mean(lp,'all');

I have made a small edit to my answer please check again. You will have 10000 mean values for each loop. It is not possible to get 51x51 mean values. Or did I misunderstand? if you want to get 51x51 mean values in the end you should have kk = 51 but it is 10000. Also in the beginning you initialize lp 1x10000 vector filled with zeros already.

BBB 2019-11-13

编辑：BBB 2019-11-13

This is my original question:

First generate 10,000 random images (i.e. where the brightness of each pixel is chosen randomly) of the same size as used in ex: 2.9(which is 51x51). For each of these stimuli, determine the firing rate (which is done by first getting the output in which you need to squeeze the rand_image_stim from 3D to 2D and then multiply with another 51x51 matrix which in this case is the gab_filt) of the cortical neuron. Then, multiply each of the stimuli with the respective firing rate (which is the jk variable here), and average the result (this is where I am getting stuck) and then plot with imagesc.

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