finding data in a matrix

Hi all,

I am in a trouble :( i do have a matrix of 251*28 that I want to extract the data by giving x and y values (columns(28) and rows(251)). ex

   ineedX = find(Xgrid >= 12 & Xgrid <=60); % the extracted data

   ineedY = find(Zgrid>= -75 & Zgrid <=-60); % the extracted data

the find command is not working when I want to apply the function as it gives a vector which I want the matrix.

any help? Thanks a lot!

Answer 1

[Bruno Luong]

Depending on how your data is organized, (you did not tell if x is first index or second) after doing

     ineedX = find(Xgrid >= 12 & Xgrid <=60); % the extracted INDEX
     ineedY = find(Zgrid>= -75 & Zgrid <=-60); % the extracted INDEX

you should do

DataExtract = Data(ineedX,ineedY)

Where Data is your original matrix. Or the reverse in indexes if you have x in second dimension.

[Lilya]

SUPER! Thanks a lot..

Answer 2

[KSSV]

A = rand(251,28) ;
A(251,28)     % this gives you 251 row and 28 column

Read about logical indexing. Don't use find.It will be slow.

Also read about ind2sub and sub2ind.

[Lilya]

Thank you so much KSSV.. ur answers are always very helpful