Error: Unable to perform assignment because brace indexing is not supported for variables of this type

Hi everybody,

if I launch this code using a single POINT it works, if instead I insert it inside a loop (with POINT that change at every iteration) this message error appears to me:

Unable to perform assignment because brace indexing is not supported for variables of this type

POINT=[x,y,z]
nRow = size(A, 1);
for iRow = 1:nRow
STRAIGHT=-20:.01:20; 
STRGT{iRow}=repmat(POINT,length(STRAIGHT),1)'+((A(iRow,:))-POINT)'*STRAIGHT;
end

How can i resolve it?

Thank's!

[madhan ravi]

STRGT=cell(1,nRow); % before loop , also move STRAIGHT outside the loop

[comment moved to answer section]

[Riccardo Rossi]

Thank you very much!

Answer 1

[madhan ravi]

STRGT=cell(1,nRow); % before the loop ,also move STRAIGHT outside the loop

[Muhammad Usman Saleem]

Why its necessary to declar an empty cell array before loop?

Why Matlab through this error when we try to declar inside loop? please

[Stephen23]

"Why its necessary to declar an empty cell array before loop? "

It is not empty, it has size 1xnRow.

The reason is to preallocate the array before the loop, thus specifying both the size and type of the array:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

Answer 2

[KSSV]

POINT=[x,y,z] ;
nRow = size(A, 1);
STRGT = cell(nRow,1) ;
for iRow = 1:nRow
    STRAIGHT=-20:.01:20;
    STRGT{iRow}=repmat(POINT,length(RETTA),1)'+((A(iRow,:))-POINT)'*STRAIGHT;
end