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Hi everybody!

I have a Matrix with 5 rows and 2300 columns M(5,2300).

0.2 0.3 0.4 2 ...

3 0.5 1.9 2.5 ...

2 0.7 0.2 3 ...

1 1 1 1 ...

0.5 0.1 1.5 3.1 ...

looks like above. The numbers you see are ratios because all the values of a particular column were divided by the value in the 4th row (which is now 1). I intend to just keep the columns for future analysis when at least one value of the other rows in a column (row1:3 and row5 values) are >=2, meaning that they should be at least the double of the value in the 4th row. As an output from the columns above it should give me an index like [1,0,0,1].

Could you probably suggest a nice solution? I'm thankful for every help.

Bruno Luong
on 14 Aug 2020

Edited: Bruno Luong
on 14 Aug 2020

Mkeep = M(:,any(M>=2,1))

Bruno Luong
on 14 Aug 2020

shouldn't call |1 0 0 1] an indexes, they form a logical array.

any(M>=2,1)

give you that.

Shae Morgan
on 14 Aug 2020

Edited: Shae Morgan
on 14 Aug 2020

do this in two steps: 1) find the indices where the values > 2 and then 2) sum the columns - if all rows 1-3 and 5 are less than 2, then this sum will be 0. If one of them has a value >=2, then the sum will be >0.

idx= M>=2;

out= sum(idx)>0

out will give you an index of 0's and 1's for each column. if 1, then it's something you should analyze later (i.e., has a value 2x row 4)

Shae Morgan
on 14 Aug 2020

single line answer by combining the variables :) Thanks for the consideration! Should work for KSSV's answer too:

out= sum(M>=2)>0 %my implementation, single line

id = find(sum(M>=2)) ; %KSSV's solution, single line

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