Automate reading multiple txt files and store it into array

[taquito]

Hi, a C newbie here.

I have been reading threads here about reading txt files into array. I simply copied a couple of useful codes from here and modified to fit my situations.

Then, I have two questions. I have a data set whose data sizes vary. let's say:

data A: 100*20 array;
data B: 180*20 array;
data C: 250*20 array;

Then, I should use fprintf and fscanf in a while loop to read from the original data and write it into a multidimensiona l array, if I understand C correctly...... (should be wrong)

Instead of defining the array size at the beginning in main(), how can I just take the array size from the data itself? I have been looking into a thread posted here a while ago, but I cannot find it. As I recall, it says:

int MAX_SIZE;
int data[MAX_SIZE][MAX_SIZE];

or something to that effect (sorry, not so specific.....)

Second question is "is there any good math/statistical library for C?"

[Ganon11]

To do this, you'd have to use pointers. You can read the X size as the first number, the Y size as the second number, then make a 2D array from a double-pointer using X and Y. Finally, you can read into the array using fscanf.

[taquito]

Please forgive me again for this simple question. I have C Primer on my desk, but it only talked about how to read a file as character.

So when I read a txt file like

FILE *fp;
double array[i][j];
int i=0,j=0;
...
...

if((fp=fopen("* **.txt","r")) == NULL)
{
printf("cannot open\n);
exit(1);
}

while
{
for (i=0;i<SIZEX; i++)
for (j=0;j<SIZEY;i+ +)

fscanf(fp,"f",& (array[i][j]);
}

Read the SIZEX as the first number (pointer) means

*SIZEX=sizeof(f p);
?

Thanks.

To do this, you'd have to use pointers. You can read the X size as the first number, the Y size as the second number, then make a 2D array from a double-pointer using X and Y. Finally, you can read into the array using fscanf.

[Ganon11]

Reading SIZEX as the first number means that, in your file, you'd have:

4
4
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

with the first 4 being SIZEX, the next 4 being SIZEY (giving you 4 * 4 = 16 values), and the rest of the numbers being your values.

You'll have to read in SIZEX and SIZEY first, before you get the values with your loops.

[taquito]

Thank you very much for your help again. I will study a bit more about malloc() and sizeof() in terms of what they do. C program is growing on me very much, and I just want to know more.... What book(s) do you reocommend to beginners and intermediate C programmers. I only have C Primer and Practical C programming at hand. Some of my friends at school recommend Numerical Recipes C. I think I need to take a look at more example codes and learn C on rtial and error. Eventually, I will move on to C++/C#. Although other friends of mine recommend learning Java, Java seems to be a bit more verbal than C/C++.

Again, thanks for your help!!!

Reading SIZEX as the first number means that, in your file, you'd have:

4
4
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

with the first 4 being SIZEX, the next 4 being SIZEY (giving you 4 * 4 = 16 values), and the rest of the numbers being your values.

You'll have to read in SIZEX and SIZEY first, before you get the values with your loops.