filling each row of a matrix using values from a vector

Question

Nora Khaled 2019-7-30

评论： Nora Khaled 2019-7-30

Hello !

I want to fell certine element in a matrix in this way:

for example matrix x=[0 0 0 0 ; 0 0 0 0 ; 0 0 0 0 ];

and then I have vector u= [1;4;3;3]

I want to use the number of in u to make x like this x=[1 0 0 0; 0 0 0 1; 0 0 1 0; 0 0 1 0];

since the first row of u contain 1 then the first row of x in the first colunm chnage to one.

and the 2nd row = 4 then x(2,4)=1.. and so one.

is there a way to do this with out loops ?

James Tursa 2019-7-30

Can we assume x starts with the proper size? In this case a 4x4 instead of the 3x4 shown.

Answer 1

James Tursa 2019-7-30

Assuming x starts as a 4x4 matrix (instead of a 3x4 matrix):

x(sub2ind(size(x),(1:numel(u))',u)) = 1;

Nora Khaled 2019-7-30

Thank you!

Although the assumption is not applicable in my case however this code seems to work.