jap7g@mendel.acc.Virginia.EDU (Jim A. Pisano) (06/04/90)
I need some ideas on reading a matrix of ASCII data quickly. I'm
developing a statistics package which reads ASCII numbers in row &
column format. The numbers can be in integer, floating point, or
scientific notation, e.g.:
1 13 82 10.4 11.0e-2
.3 0.1 4 11 12.
I've used these two bits of code, but the conversion time from the ASCII
format to an internal binary format is vey high & since I'm reading
1000's of rows of data, this can really slow things down.
/* Example 1: using fscanf() The simplest approach
*
*
*/
FILE *infp, fopen();
char *file_buf, *tbuf;
int cur_row, cur_col, rows, cols, err;
double **temp;
infp = fopen( "ascii.dat","r");
cur_row = 0;
/*
* Read "rows" number of rows of data or until we get to the end of the
* file. There are "cols" number of columns in each row. Convert a row
* at a time to an internal double matrix (which gets allocated space).
*/
cur_row = 0;
while( (cur_row < rows) && !feof(infp) )
{
for( cur_col = 0; cur_col < cols; cur_col++ ) /* read 1 row */
{
err = fscanf(infp,"%lg",&(temp_matrix[i][cur_col]));
if( err != 1 )
fprintf(stderr,"%u elements read.\n",cur_row * cols + cur_col);
}
cur_row++;
}
/* Example 2: This is a minor modification. Use fgets() to read a row
* of data to an internal temporary buffer & then use sscanf() to parse
* the numbers into the array. It goes just a little bit faster.
*/
file_buf = malloc(1025);
cur_row = 0;
while( (cur_row < rows) && !feof(infp) )
{
file_buf = fgets(file_buf,1024, infp );
tbuf = file_buf;
for( cur_col = 0; cur_col < cols; cur_col++ ) /* read 1 row */
{
err = sscanf(tbuf,"%lg",&(temp[i][cur_col]));
/*
* Skip over blanks and/or commas in data file to next number to
* process using sscanf
*/
while( *tbuf && (*tbuf != ' ') && (*tbuf != ',') )
tbuf++;
tbuf++;
if( err != 1 )
fprintf(stderr,"%u elements read.\n",cur_row * cols + cur_col);
}
cur_row++;
}
What I'd like to do is read a bunch of rows (~500) in and assign them
quickly to my 2-D double matrix "temp". But I can't figure it out.
Thanks for you help.
-Jim
____________________________________________________________________________
| |
| Jim Pisano jap7g@Virginia.EDU (jap7g@virginia.bitnet) |
| Department of Psychology uunet!virginia!jap7g |
| University of Virginia, Charlottesville, VA 22903 (804) 924-4282 |
|____________________________________________________________________________|
____________________________________________________________________________
| |
| Jim Pisano jap7g@virginia.edu |
| Department of Psychology uunet!virginia!jap7g |