normalise a column in a matrix

I have a 5x10 matrix of non-zero values. How can I normalise the 9'th column and make all its values equal to 1.

Answer 1

[Cris LaPierre]

Normalize and making all its values equal 1 are two different, non-equivalent processes.

Assuming you want to set all values to 1, something like this should work:

% Create 5x10 matrix
m=rand(5,10);
% Set all values in the 9th column equal to 1
m(:,9)=1

m = 5×10

0.0140 0.6808 0.8513 0.3171 0.7192 0.0997 0.3669 0.9666 1.0000 0.3060 0.6399 0.8033 0.3665 0.9091 0.0736 0.3212 0.0721 0.8504 1.0000 0.0836 0.9530 0.8310 0.2890 0.7311 0.5017 0.7145 0.7677 0.2626 1.0000 0.5972 0.9194 0.2587 0.6253 0.5791 0.0637 0.3085 0.7832 0.5275 1.0000 0.9422 0.1942 0.1323 0.8923 0.1072 0.5695 0.4803 0.0237 0.6503 1.0000 0.3719

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[Fadi Lama]

I want to normalize the column so that all its values are equal to one if that makes sense

(I was thinking of dividing each row by the value in the 9th column but was looking for something simpler)

[Cris LaPierre]

Ok, but the effect would be the same, right?

Divide column 9 by itself.

% Create 5x10 matrix
m=rand(5,10);
% Normalize each value in column 9 by dividing by itself
m(:,9)=m(:,9)./m(:,9)

m = 5×10

0.2220 0.3633 0.2327 0.0752 0.2392 0.0317 0.2442 0.3519 1.0000 0.7160 0.5693 0.1504 0.6034 0.5271 0.7093 0.1267 0.3073 0.8678 1.0000 0.9064 0.7947 0.9117 0.4383 0.6368 0.9732 0.0727 0.4674 0.7977 1.0000 0.9629 0.0800 0.7259 0.5368 0.5817 0.3788 0.1339 0.5561 0.0655 1.0000 0.4742 0.3518 0.1036 0.2013 0.5821 0.3154 0.0541 0.5438 0.1723 1.0000 0.4470

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btw, normalizing each row by the value that is in its column 9 is just as easy

m2=rand(5,10);
m2=m2./m2(:,9)

m2 = 5×10

0.9815 0.2271 0.2902 0.1020 0.5926 1.0735 0.3889 0.0205 1.0000 0.4472 0.7600 0.5928 0.8442 1.0917 1.2915 0.7797 0.7137 0.8735 1.0000 0.3898 16.0345 13.7806 6.8526 20.2673 1.9944 13.3427 14.5061 5.6493 1.0000 4.1880 0.0475 0.7783 0.9273 1.0538 1.0699 0.7781 0.6793 0.4814 1.0000 1.1109 0.2156 0.8290 0.1595 0.7077 0.0473 0.7178 0.6384 0.3150 1.0000 1.0240

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