Generating arrays

[rprcmky]

I have an assignment to generate two arrays of 100 values. One with a range of 0.30 - 1.00 and the other with a seed 1990*1*10. This is to be generated with a set precision of 4 decimals.

This is the first part of the assignment, I have the complete program unfinished but I'm uncertain to as if I even have this array correct.

	for(int i=0; i<100; i++)
	{
		array1[i] = (double)rand()/RAND_MAX*(1.00-0.30)+0.30;
	}
	
	srand(1990*1*10);
	for(int i=0; i<100; i++)
	{
		array2[i] = (double)rand()/RAND_MAX*(1.00-0.30)+0.30;
	}

	cout << setprecision(4) << endl;

[Azagaros]

It looks right to me if array one and two are

double array1[100];
double array2[100];

[rprcmky]

Yes they are. Now knowing that it is right, I do get results from my stats functions like mean. But they look like -3.225e-232, I should be getting numbers from 0.30 - 1.00, is something wrong with my set precision value?

Additionally, it did not look right at first because my max and min values are being outputted as 0. I have a function to sort the values in my header file that was assigned to us.

void sort(double x[], int n)
{
	// Declare objects.
	int m;
	double hold;
	
	// Implement selection sort algorithm.
	for (int k=0; k<=n-2; ++k)
	{
		// Find position of smallest value in array
		// beginning at k
		m = k;
		for (int j=k+1; j<n-1; ++j)
		{
			if (x[j] < x[m])
				m = j;
		}
		// Exchange smallest value with value at k
		hold = x[m];
		x[m] = x[k];
		x[k] = hold;
	}
	
	return;
}

and this is what I have in my main file

	void sort(double array1[100], int array1);
	void sort(double array2[100], int array2);
	cout << setprecision(4) << array1 << endl;

int is referring to the integers in array1 and array2 so it should sort and set the values within 4 decimals for all 100 values correct?

I think I need to create a search index? Which I think is put in the beginning where I assign my variables which would be

	double array1[100], array2[100], max1, min1, mean1, med1,
		var1, stddev1, max2, min2, mean2, med2, var2, stddev2;
	int search_index;
		search_index = search(array1, 100, 0.725);

I'm almost there...

[Azagaros]

I don't think there is anything wrong with your precision value. I am wondering if your use of Rand() is wrong.

could you tell me the value of RAND_MAX?

The test I ran On just the random values with a arbitrary number didn't give me anything near that value range and the two numbers I tried were 70 and .7

I even tried, which gave me the range I wanted but not to 4 places:

(double)(rand() % 70 + 30)/100

I just tried a test like:

#include <iostream>
#include <cstdlib>

using namespace std;

int main()
{
    double ArrayOne[100];

    for(int i = 0; i < 100; i++)
    {
        ArrayOne[i] = (double)(rand() % 70 + 30)/100;
//        ArrayOne[i] = (double)rand()/.7*(1.0-0.3)+0.3;
        cout << i << ": " << ArrayOne[i] << endl;
    }
}

and your equation I got numbers completely out of range.

I thought they looked right but I had to test them to be sure.

[rprcmky]

I think I figured out the problem I had. It wasn't that my array wasn't generating the random values and the random values for array 2 with the seed.

In my second attempt, I changed my set precision output to
cout << setprecision(4) << array1 << endl;
where I had array1, thinking it would set the value to 4 decimals to array1. If I just took it out, the set precision would output for all arrays above right? Doing this will give me my output values correctly instead of the -3.345e-434 I was getting?

Additionally, when finding the min and max values of my array, I had used the sort function provided using my header file.

I had

	void sort(double array1[100], int array1);
	void sort(double array2[100], int array2);

which needs to be

	sort(array1, int 100);
	sort(array2, int 100);

Will try these changes when I get home tonight, this is more or less for verficiation and noting the changes to look back on.

[rprcmky]

The mistake in my cout was not the problem. I'm still getting back odd numbers such as -3.225e-323 and 0's for my max/min values. The value for RAND_MAX is something along the lines of 32,xxx isn't it?

array1 should be generating numbers from 0.30 - 1.00 without a seed, so we should be getting values in the same order.

This is what I have now.

	double array1[100], array2[100], max1, min1, mean1, med1,
		var1, stddev1, max2, min2, mean2, med2, var2, stddev2;
	
	for(int i=0; i<100; i++)
	{
		array1[i] = ((double)rand())/(RAND_MAX*(1.00-0.30)+0.30);
	}
	
	srand(4003);
	for(int i=0; i<100; i++)
	{
		array2[i] = ((double)rand())/(RAND_MAX*(1.00-0.30)+0.30);
	}
	sort(array1,100);
	sort(array2,100);
	cout << setprecision(4) << endl;

[rprcmky]

anyone?

[ne555]

¿How are you printing the arrays? (and obtainning the other values)

//array1[i] = ((double)rand())/(RAND_MAX*(1.00-0.30)+0.30);
//the parenthesis are wrong

double random = ((double) rand())/RAND_MAX; // -> [0;1]
return random*delta + inic;

[rprcmky]

Using functions to get information from the array

	cout << "Values for Array 1" << endl;
	
        maxval(array1, max1);
	cout << "Maximum Value: " << max1 << endl;
	
        minval(array1, min1);
	cout << "Minimum Value: " << min1 << endl;
	
	mean(array1, mean1);
	cout << "Mean: " << mean1 << endl;
	
	median (array1, med1);
	cout << "Median: " << med1 << endl;
	
	variance(array1, var1);
	cout << "Variance: " << var1 << endl;
	
	std_dev(array1, stddev1);
	cout << "Standard Deviation: " << stddev1 << endl << endl;

Am I not calling the functions correctly?
This is what is in my header file.

double maxval(const double x[], int n);
double minval(const double x[], int n);
double mean(const double x[], int n);
double median(const double x[], int n);
double variance(const double x[], int n);
double std_dev(const double x[], int n);

[ne555]

double maxval(const double x[], int n); The parameters are the array, and the number of items that the array holds.
The function returns the maximum value.
max1 = maxval(array1, 100);

[rprcmky]

Understood. So additionally, a search index function like
int search(const double A[], int n, double value);
is the function, of the arbitrary array, # of items of array, and the value to be indexed?
would look like

	searchval = search(array1, 100, 0.725);
	cout << "The index of 0.725: " << searchval << endl << endl;

Where I have searchval declared as an int in the beginning of the program?