A blank program

[storygeek]

Situation: I typed down a code that's supposed to calculate statistics of the population with given values. There's no errors but when I run it I get a blank empty screen. I typed in the values but it still wouldn't work. Vertically and horizonally. And Horizonally split up with commas. Anybody's help would be greatly appreciated.

 

[ArkM]

Where is your (minimal) code? Can we answer to absolutely abstract questions?..
I have a car. I can't use it. Whay's a problem? Help me, please...

 

[storygeek]

#include <stdio.h>
#include <math.h>
main()
{
float x,/*current value input*/
max,
min,
sum,
mean,
sum_of_squares,
variance;
int count;

if (scanf("%f", &x) == EOF ) /* EMPTY? */
printf( "0 data items read\n");
else {
max = min = sum = x;
count = 1;
sum_of_squares =x * x;
while (scanf("%f", &x) != EOF)
{
count += 1;
if (x > max) /*new high?*/
max = x;
if (x < min) /* new low?*/
min = x;
sum += x;
sum_of_squares += x * x;
}
printf( "%d data items read\n", count);
printf("maximum value read = %f\n", max);
printf("minimum value read = %f\n", min);
printf( "sum of all values read = %f\n", sum);
mean = sum / count;
printf ("Mean = %f\n", mean);
variance = sum_of_squares / count - mean * mean;
printf("variance = %f\n", variance );
printf( "standard deviation = %f\n",
sqrt (variance));
}
}
I'm showing the whole program since I can't trace where the problem is.

 

[SwapSawe]

Hi !!!

Please see this extract of 'man scanf()'.

The value EOF is returned if an input failure occurs before
any conversion such as an end-of-file occurs. If an error or
end-of-file occurs after con-version has begun, the number of
conversions which were successfully completed is returned.


Since your function never encounters a failure before conversion it does not reach EOF. remember: An empty input is not an input failure, in that case scanf would not return EOF. To Return EOF please press control-D, if you are using *nix Environment. If you are using DOS/Windows, please excuse.

Regards,
SwapSawe.

 

[ArkM]

SwapSawe is right. On Windows press Ctrl-Z to terminate console stdin.
It seems more better using (scanf(...) != 1) stop condition. Initialize all variables then use scan loop:

float x,
      mean = 0,
...
      ;
int   count;
if (scanf(...) != 1)
{
   /* fail: no values or errors */
   exit(1);
}
minval = maxval = x;
for (count = 1; scanf(...) == 1; ++count)
{
  /* increase sum vars etc */
}
if (count > 1)
{
   /* calculate and print */
}
else /* only 1 value report */

Avoid using min and max as var names: there are library functions/macros with that names...
As far as I know a true estimation of variance is

D = (1/(n-1))*sum((xk - M)^2);

Consult your math stat book...

Use doubles instead of floats (correct scanf format spec to %lf): float arith is slower than double on most of CPU and printf args automatically converted in doubles (what for in that case?).

Add else before if (x < minval): no need to check this cond when 1st if cond was true...