Thread: Max Min Problem

So here I am writing this code and I am having problems with something basic, but I think I am overlooking something simple. I am trying to read from a text file and compute mean, root mean, and Max height (which is the highest number - lowest number) It's coming up with some huge number so yea, I need a second opinion please! Here is the data file

Code:

-4.1 -2.2 -0.5  1.2  3.3  4.6  5.1  2.1  0.2 -3.6 -4.1  0.2
 0.5  2.2  4.1 -0.2 -1.2 -3.3 -4.6 -5.0 -2.2 -1.1  0.8	3.2
-0.1 -4.8

And here is the Code

Code:

/* Christopher R Smith
COMP1200 - Fall 2008
Assignment 6
Program: Average Value Program

-------------------------------------------------------------------------------------------------------------
Taking surface measurements from a text file, compute and display the Arithmetic Mean Value, the
Root Mean Square Average, and the Max Roughness Height

--------------------------------------------------------------------------------------------------------------
*/

#include <stdio.h>
#include <math.h>

int main()
{
FILE 		*inp;
double	value, 	
			mean,
			root_mean_square,
			sum=0,
			max_height;
int 		numValue=0,
			count;
		

inp = fopen("surface.txt", "r");		

while ( ( fscanf ( inp,"%lf", &value ) ) == 1 )
	{
		  sum += fabs(value);
		  numValue++;
		  
	}

mean = sum / numValue;

while ( ( fscanf ( inp,"%lf", &value ) ) == 1 )
	{
		  sum += pow( fabs(value), 2 );
		  numValue++;
		  
	}

root_mean_square = sqrt( sum / numValue);



while ( ( fscanf ( inp,"%lf", &value ) ) == 1 )
	{
		double max=-10000, min=10000;

				
				if (value >= max)
						max = value;
				else 
						min = value;
							
		;
			max_height = max - min
	}
		

	
printf( "Arithmetic mean value %.2lf\n", mean);
printf( "Root-mean-square average %.2lf\n", root_mean_square);
printf( "Maximum roughness height %.2lf\n", max_height);					







return (0);
}

This problem is probably coming from this segment of code

Code:

while ( ( fscanf ( inp,"%lf", &value ) ) == 1 )
	{
		double max=-10000, min=10000;

				
				if (value >= max)
						max = value;
				else 
						min = value;
							
		;
			max_height = max - min
	}

I am receiving this output

Code:

Arithmetic mean value 2.48
Root-mean-square average 1.58
Maximum roughness height 1889828851749420549890302903237191694835027000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.00

Is that huge number some other value somewhere else in the computer

what if we aren't supposed to "know" how to make a user defined function like you did in

Code:

double MAX ( double a, double b )

and

Code:

double MIN ( double a, double b )

I am not sure if understand this part of the code

Code:

double MAX ( double a, double b ) 
{
  return a > b ? a : b;
}

double MIN ( double a, double b )
{
  return a < b ? a : b;
}

the

Code:

? a : b;

That's the ternary operator: It's shorthand for an if-else. Feel free to ignore that and use an actual if-else in your code.

>> What happens if you pass NaN to one of those functions?
At a stab in the dark, I'm guessing it breaks, otherwise you wouldn't have mentioned it. But correct me wherever possible. And admittedly I did not consider NaNs while helping this lad with his assignment.