Converting the format Row Column Value into matrix ?

Hi everyone. The question as the title says is that i have an input text file which is in the format row-number column-number value and it has to be converted into a matrix

for example if the test.txt is

1 2 5
1 3 6
2 1 8
2 5 1
3 1 4
3 3 2

this will convert to

0 5 6 0 0  
8 0 0 0 1  
4 0 2 0 0

I was looking through the matrix indexing but i am very confused here. It would be great if someone could help me out here! Thanks!

p.s: Also note that there will be no overrides for any value in the matrix

edit: fixed the typo in the sample output

[Azzi Abdelmalek]

How the result is related to your data?

[rya11111]

Well the first number of the text file is the row number

the second number in the line is the column number

and the last the value of the corresponding row and column

any value not specified is considered as 0 and the maximum number of columns in the matrix is the highest column number of some row

Answer 1

[Geoff Hayes]

The following uses a for loop but that should be fine for this problem:

 % load the data
 A = importdata('test.txt');

 % use max to determine the row and column dimension of the output matrix
 dims = max(A);

 % size the output matrix
 mtx = zeros(dims(1),dims(2));

 % iterate over each row of A and assign to the appropriate entry in mtx
 for k=1:size(A,1)
     mtx(A(k,1),A(k,2)) = A(k,3);
 end

The answer, given your data, is

 mtx =
     0     5     6     0     0
     8     0     0     0     1
     4     0     2     0     0

Almost the same as yours except for the 2 replaces your 3.

[rya11111]

Sorry for the typo :D

I will check this soon and let you know the outcome! thanks a lot!

Answer 2

[Matt J]

S = spconvert(load('test.txt','-ascii'));

[Matt J]

You can then convert the matrix to full form if desired,

    S=full(S);

but normally the original sparse form is what you want.

[rya11111]

Thank you so much for taking time to help out!

Answer 3

[Azzi Abdelmalek]

A=[1 2 5
   1 3 6
   2 1 8
   2 5 1
   3 1 4
   3 3 2]
n=max(A(:,1))
m=max(A(:,2))
out=zeros(n,m)
out(sub2ind([n m],A(:,1),A(:,2)))=A(:,3)

[rya11111]

Thank you so much for taking time to help out!

Answer 4

[Andrei Bobrov]

A = [1 2 5
1 3 6
2 1 8
2 5 1
3 1 4
3 3 2];

out = accumarray(A(:,1:2),A(:,3))

[rya11111]

Thank you so much for taking time to help out!