[英]Reading CSV file to 2D double array in C
I need to write a program to parse a large CSV file (approx. 2000*2000) in C and store in the form of a double[] [] array. 我需要编写一个程序来解析C中的大CSV文件(大约2000 * 2000),并以double [] []数组的形式存储。 I wrote a program, which seems to work for small files (i checked for a 4*4 csv file), but for large files it gives me incorrect results.(as in the number of rows and columns are wrong and the program crashes after that).
我写了一个程序,该程序似乎适用于小文件(我检查了4 * 4的csv文件),但是对于大文件,它给了我错误的结果(因为行数和列数错误,并且程序在崩溃后崩溃了)那)。
This is the code: 这是代码:
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main (void)
{
int rowMaxIndex,columnMaxIndex;
double **mat;
double *matc;
int i,j,idx,len;
char part[5000];
char *token;
char *temp;
char *delim = ",";
double var;
{
FILE *fp;
fp = fopen("X1_CR2_new1.csv","r");
if(fp == NULL)
{
perror("Error while opening the file.\n");
exit(EXIT_FAILURE);
}
// count loop
rowMaxIndex = 0;
columnMaxIndex = 0;
while(fgets(part,5000,fp) != NULL){
token = NULL;
token=strtok(part,delim);
while(token != NULL){
if(rowMaxIndex==0)
{
columnMaxIndex++;}
token=strtok(NULL,delim);
}
rowMaxIndex++;
}
fclose(fp);
printf("Number of rows is %d, and Number of columns is %d", rowMaxIndex, columnMaxIndex);
// allocate the matrix
mat = malloc(rowMaxIndex * sizeof(double*));
for (i = 0; i < rowMaxIndex; i++)
{
mat[i] = malloc(columnMaxIndex * sizeof(double));
}
fclose(fp);
}
// rewind the file to the beginning. The rewind(fp) wasnt working so closed and reopened file.
{
FILE *fp;
fp = fopen("X1_CR2_new1.csv","r");
if(fp == NULL)
{
perror("Error while opening the file.\n");
exit(EXIT_FAILURE);
}
// read loop
i = j = 0;
while(fgets(part,5000,fp)!=NULL)
{
token=strtok(part,delim);
j=0;
while (token != NULL){
mat[i][j]=atof(token);
//printf("\n %f", mat[i][j]);
token=strtok(NULL,delim);
j++;
}
i++;
}
printf("\n The value of mat 1, 2 is %f", mat[1][0]); //print some element to check
free(mat);
fclose(fp);
}
return 0;
}
You say you data has 2000 columns but your fgets()
reads at most 4999 characters. 您说数据有2000列,但
fgets()
最多读取4999个字符。 Isn't there a chance your data is wider than 4999 chars? 您的数据是否有可能超过4999个字符? You should probably check that each line read in ends with a newline (except perhaps the last line in the file).
您可能应该检查读入的每一行是否以换行符结尾(也许文件中的最后一行除外)。
As an aside, you don't need to reopen the file--just rewind()
it. 顺便说一句,您不需要重新打开文件-只需
rewind()
。
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