To all,

 

I am undergoing an analysis involving big matrices of about 30000x200 which
I have to handle in a more efficient way. So I would like some advice to
build such efficient function to deliver the following result:

 

-          starting with 2 matrices of the same dimension (eg. A and B)

 

       0  0  3  5                      6  0  0  5 

A=   0  0  6  4              B=   0  4  3  5

             0  0  5  0                      1  0  0  9  

 

-          the function should deliver a C matrix (same dimension too),
where at each position C(i,j), compares A and B. 

      if A(i,j)=0, than C(i,j)=0, 

      if A(i,j)!=0, than C(i,j)=B(i,j) 

 

      6  0  0  5

C= 0  0  3  5

 0  0  0  0

 

Although not an expert I could build a function with 2 cycles (reading
columns and rows) which is not quick. Maybe you can help me in this
“challenge”.

 

Much thanks in advance,

 

 
Diogo André Alagador
Biodiversity & Global Change Lab, Museo Nacional de Ciencias Naturales,
CSIC, Madrid, España
Forest Research Centre, Instituto Superior de Agronomia, Universidade
Técnica de Lisboa, Lisboa, Portugal
 

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