# I need to replace an enitre row, if any of the value goes less than zero

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Suman on 23 Feb 2015
Edited: Hikaru on 24 Feb 2015
I need to check each row, whether is there any of the value less than zero in a particular row. If any value in a row is less than zero, i have to replace the entire row itself.
For example,
a1=[1 2; 3 4; -5 6] a2=[22 23; 56 78; 89 75]
Step 1: I need to check whether any element of a row is less than zero in matrix a1...... Step 2: If there is any negative value, i have to replace that particular row by the the same row of the another matrix a2.
Problem with the coding I did, If there is only one negative value in a row, then the negative value only is replaced by the another matrix of the same (row,column), but I couldn't replace the entire row.

Hikaru on 23 Feb 2015
This will solve it.
a1=[1 2; 3 4; -5 6]
a2=[22 23; 56 78; 89 75]
neg = a1<0 % return '1' for values less than zero
a1(neg,:) = a2(neg,:) % step 2
Hikaru on 24 Feb 2015
Edited: Hikaru on 24 Feb 2015
Now that I redo this problem with another matrix, the solution above does not work if the negative value is located in the second column.
Assuming you have matrix of 2 columns only, you might want to try the code below:
neg1 = a1(:,1)<0
neg2 = a1(:,2)<0
neg = neg1|neg2
a1(neg,:) = a2(neg,:)
I haven't fully tested it, but it should give you a start. Like Stephen said, you need to be more specific for a more specific solution.

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