i have 4 columns of (256x4 double) type.

I want to add column 1 with 3 and column 4 with 2 and need to store results in two columns. In first column it should save the result of 1 and 3 and in second column it should save 2 and 4 result. one more thing i want to add column 1 with 3 randomly.Like 1st index of column 1 need to add with any index of column 3. i don't want to add these columns with similar index

Answer 1

[Roger Stafford]

B = A(:,1:2)+A(:,3:4);

[mania online]

but result is in three columns. It should be in two columns

[mania online]

can you please be more specific..

[Image Analyst]

A = rand(8,4);
B = A(:,1:2)+A(:,3:4)

B =
      0.98629       1.3985
      0.80086      0.72194
      0.37316       1.3508
       1.5032        1.019
       1.3499      0.93814
      0.47971      0.74486
       1.0692      0.95154
      0.53281       1.3454

See - just two columns, not three.

[mania online]

i m getting three... i dont know why

[mania online]

I have positive numbers in four columns

[Star Strider]

Post your code.

[mania online]

i can't post whole code here because output is the result of multiple functions

[mania online]

[mania online]

after RED =I4(:,1:3)+I4(:,2:4); i get

[Star Strider]

Post the code you use to add the columns of your matrices.

[mania online]

 RED =I4(:,1:3)+I4(:,2:4);

[mania online]

one more thing i want to add column 1 with 3 randomly.Like 1st index of column 1 need to add with any index of column 3. i don't want to add these columns with similar index

[Image Analyst]

When you say I4(:,1:3), that's getting 3 columns. When you say I4(:,2:4), that's getting 3 columns.

Look

1:3 = [1,2,3]

2:4 = [2,3,4]

See, that's 3 columns, not 2. Why did you do that instead of the code Roger gave you? Roger's code gives you what you originally asked for, so use 1:2 and not 1:3.

[mania online]

got the point. Can you please tell me how to add column 1 with 3 randomly.Like 1st index of column 1 need to add with any index of column 3. i don't want to add these columns with similar index.

[Roger Stafford]

I interpret your statement "add column 1 with 3 randomly.Like 1st index of column 1 need to add with any index of column 3. i don't want to add these columns with similar index" to mean that you seek a random permutation of column 3 which at no position from 1 to 256 does the permuted index value agree with the original position index value. For columns of length 256 the while-loop in the code below will probably require an average of two to four repetitions. If you wish the same action for columns 2 and 4, the following code can easily be modified to do that.

n = size(A,1);
b = true;
while b
  p = randperm(n);
  b = any(p==(1:n));
end
B(:,1) = A(:,1) + A(p,3);