matlab : Inserting elements in array

Question

This is really basic question. I have an array "relevant_IDs". I need to store 1 to 100 values in it when variable category is 1. Similarly, 101 to 200 when category is 2. So on till 901 to 1000 when category is 10. I have written code for it but it is not inserting 100 values in it.

Code:
for i=1: 1000 
     if(category==1 && i>0 && i< 101)
      relevant_IDs(i) = i;
     end
     if(category==2 && i>100 && i< 201)
      relevant_IDs(i) = i;
     end
     if(category==3 && i>200 && i< 301)
      relevant_IDs(i) = i;
     end
     if(category==4 && i>300 && i< 401)
      relevant_IDs(i) = i;
     end
     if(category==5 && i>400 && i< 501)
      relevant_IDs(i) = i;
     end
     if(category==6 && i>500 && i< 601)
      relevant_IDs(i) = i;
     end
     if(category==7 && i>600 && i< 701)
      relevant_IDs(i) = i;
     end
     if(category==8 && i>700 && i< 801)
      relevant_IDs(i) = i;
     end
     if(category==9 && i>800 && i< 901)
      relevant_IDs(i) = i;
     end
     if(category==10 && i>900 && i< 1001)
      relevant_IDs(i) = i;
     end

  end

AnonSubmitter85 · Accepted Answer · 2014-10-14 04:01:27Z

2

Something like this should work and be much quicker:

relevant_IDs = (category - 1) * 100 + (1:100);

answered Oct 14, 2014 at 4:01

AnonSubmitter85

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Comments

Amro · Accepted Answer · 2014-10-14 06:29:19Z

1

You could also just generate the whole thing (numbers from 1 to 1000), then index into the matrix using category value as index to get the desired relevant_IDs:

relevant_IDs = reshape(1:1000, [100,10]).';
relevant_IDs(category,:)    % this will return a 1x100 row vector
                            % (category is a number from 1 to 10)

answered Oct 14, 2014 at 6:29

Amro

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