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How to find values in one vector that don't have corresponding values (in the same row) in another

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Emily Cooper
Emily Cooper on 2 Jul 2019
Answered: SaiDileep Kola on 16 Jul 2019
I have a very large dataset of sample measurements and I need to plot sample data but without the 'background' data, i.e. data that appears in the control samples. Here is an example of the data:
row a b c sample1 sample2 control1
1 5 2 1 236489 NaN 456932
2 8 3 0 NaN 278695 569202
3 12 8 2 NaN 332465 NaN
I have loaded the whole dataset as a tab delimited txt file and so each column of data is in a different vector. (NaN is where there was no value in the original tab file).
I need to plot a/b against c/b with the sample value on the z axis. I have managed to do this for all the values in the sample vector, but I need to remove all the sample values that have a value on the same row in the control sample. For example, if I want to plot the data for sample2 that does not occur in control1 I have this:
ab = a(:,1)./b(:,1);
cb = c(:,1)./b(:,1);
sample2_without_control1 = setdiff(sample2,control1)
What I would aim to plot is the a/b and c/b values but only from row 3 - as this is the only row in which there is data from sample2 but not control1. However setdiff doesn't work - I still need the value to be kept the same (i.e. as 332465) and not altered at all.
(I have thousands of rows of data like this, so I need a way to do this for entire vectors at once please!)
Thank you :)


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Emily Cooper
Emily Cooper on 2 Jul 2019
I tried that. It works but just gives a binary output in 1 and 0 for where a value occurs/doesnt occur. I need to keep the values as they are, if thats possible. Thank you though!
Adam on 2 Jul 2019
Which bit gives a binary output?
You will lose the exact positions for your
result, but these can just be reinserted into a full length vector of NaNs or whatever you want for the non-results again afterwards, using the same idx vector for their positions.
Jan on 2 Jul 2019
I do not understand, what you are asking for. "setdiff doesn't work" - what does this mean? Of course setdiff is working.
You want to get the indices of some rows. So do not use a = setdiff(b,c) but the 2nd output also.
"I need to remove all the sample values that have a value on the same row in the control sample" - this might mean:
keep = not(ismember(sample1, control1) | ismember(sample2, control1));
ab = a(keep,1) ./ b(keep,1);
cb = c(keep,1) ./ b(keep,1);
scatter3(ab, cb, sample2(keep))

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Answers (1)

SaiDileep Kola
SaiDileep Kola on 16 Jul 2019
Hi Emily,
Please first find the indices of the matrix with control1 values as NaN using the following command:
indices = find(isnan(your_matrix(:,control1)) == 1)
You can also use the 'nansum' comment to add values of sample1 and sample2 in a row-wise fashion:
y = nansum(X,2) %2 is to add along column dim
X is your reformed matrix after removing rows with NAN values and containing only sample1 and sample2 columns
Now you can plot accordingly


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