I'm trying to initialize an array of floats that are made up of x and y
coordinates. I want to make these coordinates match a curvy pattern of
Is summer school already in session?
some sort if they were plotted on a 2d plane so that I don't have to
write each array index by hand. I don't care what the pattern looks
like, just so that it has some bends, curves, etc...
Anyone know how this would be generated?
You need to know what kind of shape that you want and choose an equation
for it.
float x[1000];
float y[1000];
An array of coordinate structures might be more useful:
struct coordinate {
float x;
float y;
};
array = struct coordinate array[1000];
but stick to your arrays. The equation for a circle is:
y = sqrt((power(radius, 2) - power(x, 2))
Note that there are two possible y's (on positive and one negative) for
every x. That means you really only need 500 hundred x values to give you
1000 data points. Half will give a you a radius of 250 with integer x
values:
00:53,511$ cat circle.c
#include <stdio.h>
#include <math.h>
int main() {
const double radius = 250;
/* note; an array of coordinate structs might be more descriptive
* */
double x[1000], y[1000];
int current_x = -250;
int i;
/* calculate the cooridents */
for (i = 0; i < 1000; i += 2) {
/* save the x values */
x
= (double) current_x;
x[i+1] = (double) current_x;
/* calculate the y values */
y = sqrt(pow(radius, 2) - pow((double) current_x, 2));
y[i+1] = sqrt(pow(radius, 2) - pow((double) current_x, 2))
* -1;
/* move on to the next x */
current_x++;
}
/* print the coordinates */
for (i = 0; i < 1000; i += 1)
printf("%f\t%f\n", x, y);
return 0;
}
00:53,512$ gcc -lm -o circle circle.c
00:53,513$ echo '
set terminal dumb 60 60
set xrange [-275:275]
set yrange [-275:275]
plot "< ./circle" using 1:2
' | gnuplot
+------+--------+---------+--------+--------+------+
| + + "< ./circle" using 1:2 + A |
| |
| AAAAAAAAAAAAAA |
| AAA AAA |
| AAA AAA |
| AAA AAA |
| AA AA |
200 ++ AA AA ++
| AA AA |
| AA AA |
| AA AA |
| AA AA |
| AA AA |
| A A |
| AA AA |
| A A |
| AA AA |
100 ++ A A ++
| A A |
| AA AA |
| A A |
| A A |
| A A |
| A A |
| A A |
| A A |
| |
0 ++A ++
| |
| A A |
| A A |
| A A |
| A A |
| A A |
| A A |
| AA AA |
| A A |
-100 ++ A A ++
| AA AA |
| A A |
| AA AA |
| A A |
| AA AA |
| AA AA |
| AA AA |
| AA AA |
| AA AA |
-200 ++ AA AA ++
| AA AA |
| AAA AAA |
| AAA AAA |
| AAA AAA |
| AAAAAAAAAAAAAA |
| |
| + + + + + |
+------+--------+---------+--------+--------+------+
-200 -100 0 100 200
00:54,514$
You can any other equation in a similar manner:
01:08,529$ cat third.c
#include <stdio.h>
#include <math.h>
int main() {
double x[1000], y[1000];
double current_x = -2;
int i;
/* calculate the cooridents */
for (i = 0; i < 1000; i++) {
x = current_x;
y = pow(current_x, 3) - (4 * current_x);
current_x += .004;
}
/* print the coordinates */
for (i = 0; i < 1000; i++)
printf("%f\t%f\n", x, y);
return 0;
}
01:08,530$ gcc -lm -o third third.c
01:08,531$ echo '
set xrange [-4:4]
set yrange [-4:4]
set terminal dumb 60 60
plot "< ./third" using 1:2
' | gnuplot
4 ++-----+-----+------+------+-----+------+-----+-----++
+ + + + "< ./third" using 1:2 + A +
| |
| |
| |
| |
| A |
3 ++ AAA ++
| A AA |
| A A |
| AA AA |
| A A |
| A A |
| A AA |
2 ++ AA A ++
| A A |
| A AA |
| A A |
| A A |
| AA A |
| A AA |
1 ++ A A ++
| A A |
| A A |
| A AA |
| A A |
| AA A |
| A A |
0 ++ A AA A ++
| A A |
| A AA |
| A A |
| AA A |
| A A |
| A A |
-1 ++ A A ++
| AA A |
| A AA |
| A A |
| A A |
| AA A |
| A A |
-2 ++ A AA ++
| AA A |
| A A |
| A A |
| AA AA |
| A A |
| AA A |
-3 ++ AAA ++
| A |
| |
| |
| |
| |
+ + + + + + + + +
-4 ++-----+-----+------+------+-----+------+-----+-----++
-4 -3 -2 -1 0 1 2 3 4
01:08,532$
