1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
double SumArray ( double [ ], int );
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define SQUARE(x) ((x)*(x))
// Defing a specific format for the listing instead of using
// multiple tabs
#define W "15"
#define Z "14"
#define U "%"Z"s"
#define S "%"W"s"
#define F1 "%"W".1f"
#define F2 "%"W".2f"
/* SumArray is a fonction that calculates the sum of any
array when it is called */
#include "rent.h"
double SumArray (double a[], int n)
{
int c;
double sum = 0;
for (c = 0; c < n; c++)
{
sum += a[c];
}
return sum;
}
#include "rent.h"
int main (void)
{
// Two arrays that are the ones provided from the file
double filearray1[14], filearray2[14],
// Three arrays to store in them further calculations
filearray3[14], filearray4[14],
filearray5[14];
// Setting counter to 0
size_t r = 0;
FILE *fp;
// File that we will read from
char fname[] = "rent2.dat";
if ((fp = fopen (fname, "r")) == NULL)
{
printf ("Unable to open %s.\n", fname);
exit (1);
}
printf (S S "\n", "Rent","Income");
printf (U U U U U "\n", "X","Y","X^2","Y^2","XY");
while (r < (sizeof filearray1/sizeof *filearray1 )
&& fscanf (fp, "%lf%lf\n", &filearray1[r], &filearray2[r]) != EOF)
{
// The three arrays which contain calculations:
// Squaring the first array read and storing it in another one
filearray3[r] = SQUARE (filearray1[r]);
// Doing the same thing with the second one
filearray4[r] = SQUARE (filearray2[r]);
// Product of the first two arrays
filearray5[r] = filearray1[r] * filearray2[r];
// Priting everything
printf (F1 F1 F2 F2 F2 "\n",
filearray1[r], filearray2[r], filearray3[r],
filearray4[r], filearray5[r]);
r++;
}
// Summing all the arrays and storing results
// in new double variables so that further
// will be easier
double SumX = SumArray (filearray1,r),
SumY = SumArray (filearray2,r),
SumXX = SumArray (filearray3,r),
SumYY = SumArray (filearray4,r),
SumXY = SumArray (filearray5,r);
printf (S S S S S "\n", "------","--------","---------","-------------","-----------");
// Printing the total at the end of each array
printf (F1 F1 F1 F1 F1"\n", SumX, SumY, SumXX, SumYY, SumXY);
printf("\n\n\t\t\t Press ENTER to Continue");
getchar();
/* Coefficient of correlation calculations */
// Number of elements contained in each array
int N = 14;
// Variable of the coefficient
double coef;
// Declaring two others so that the formula is easier
double coef1, coef2;
// Calculation of the coefficient using formula provided
coef1 = N*SumXY - (SumX)*(SumY);
coef2 = sqrt((N*SumXX - SumX*SumX)*(N*SumYY - SumY*SumY));
coef = coef1/coef2;
printf ("\n\n\t +=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+ ");
printf ("\n\t | Coefficient of correlation is: | ");
printf ("\n\t | r = + %.2lf | ", coef);
printf ("\n\t +=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+ \n");
/* Regression equations calculation */
// Variables needed for the equation
double a, b, b1, b2, avgX, avgY;
// Averaging X and Y
avgX = SumX/N;
avgY = SumY/N;
// Calculating b
b1 = SumXY - N*avgX*avgY;
b2 = SumXX - N*avgX*avgX;
b = b1/b2;
// Calculating a
a = avgY - b*avgX;
// Plugging a and b and priting the equation
printf("\n\t Regression equation is: \n");
printf("\t =-=-=-=-=-=-=-=-=-=-=-= \n");
printf("\n\t Yc = a + bX = %.2lf + %.2lfX\n", a, b);
printf("\n\t( a = %.6lf , b = %.6lf )\n\n", a, b);
/* Stand error of estimate */
double Sy;
Sy = (SumYY - (a*SumY + b*SumXY))/N;
Sy = sqrt (Sy);
printf("\t +=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=+ ");
printf("\n\t | The Standard error of estimate: |");
printf("\n\t | Sy = +/- $%.2lf |", Sy);
printf("\n\t +=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=+\n");
printf("\n\t\t\t Press ENTER to continue \n");
getchar();
// Variables needed for prediction of the income
double rent, choice, income, lower, upper;
do
{
printf("\n\nEnter a rent amount (to quit enter 0) : ");
scanf("%lf", &rent);
if(rent > 0)
{
income = a + (b*rent);
lower = income - Sy;
upper = income + Sy;
printf("\n\n\t Rent \t\t Lower Limit \t Predicted Income \t Upper Limit \n");
printf("\n\t$ %.2lf \t %.2lf \t %.2lf \t\t %.2lf \n", rent, lower, income, upper);
}
else if ( rent < 0 )
{
printf("\nError! Entry not valid, try again.\n");
}
}
while (rent != 0);
return 0;
} |
