Import data of form <<(index, index) value>> into sparse matrix

I've got a plain text data file (.dat) containing sparse matrix information that I'd like to import into MATLAB. It looks a bit like:

(1,2)    1    
(2,3)    2

And so forth, where we've got the index for matrix position in the left hand column, and the value to go there in 开发者_C百科the right. Searching around hasn't turned up a nice and easy way to do this, but I don't have an overwhelming amount of experience with MATLAB, so I don't know if I'm missing something obvious.

You can use function spconvert

Examples:

Suppose the ASCII file uphill.dat contains

1    1    1.000000000000000
1    2    0.500000000000000
2    2    0.333333333333333
1    3    0.333333333333333
2    3    0.250000000000000
3    3    0.200000000000000
1    4    0.250000000000000
2    4    0.200000000000000
3    4    0.166666666666667
4    4    0.142857142857143
4    4    0.000000000000000

Then the statements

load uphill.dat    
H = spconvert(uphill)

H =

   (1,1)       1.0000
   (1,2)       0.5000
   (2,2)       0.3333
   (1,3)       0.3333
   (2,3)       0.2500
   (3,3)       0.2000
   (1,4)       0.2500
   (2,4)       0.2000
   (3,4)       0.1667
   (4,4)       0.1429

You can try using scanf. Here's some code to start with:

fid = fopen('sparse.dat', 'rt');
[m n] = fscanf(fid, '(%d,%d) %d\n');
fclose(fid);
m = reshape(m, 3, length(m)/3)';
% m should now be:
% [1 2 1; 2, 3, 2]