Determining time (x) increments between y-values on a sine wave

Projects Programming
1

I'm trying to figure out the x-increments between the integer values of y, of the function:

y = 72sin(x-[PI/2])+72, and enter them into an array of length 144, which is how many integer y-values there should be.

Any idea how best to achieve this?

2

Since sin() returns a float or double, the result, or any integer multiple of the result, will almost never be an exact integer.

Instead, you need to decide whether a given value can be considered "close enough" to an integer, by some criterion.

e.g.

int y = x;
if ( fabs(x - y) < 0.01) Serial.println("close enough");

Or just round off the result to the nearest integer, if it is for a display.

3

I'm at this point:

#include "Math.h"

float y;

void setup() {
Serial.begin(115200);
}

void loop() {

for (int i = 0; i < 144; i++){
y = ((asin((i-72)/72)+(PI/2))/PI);
Serial.println(y);
delay(100);
}


...but the Serial Monitor is returning a "y" value of 0.50 for all but one value, the first one, for which it returns 0.
4

This is integer math. No wonder you are seeing low value integers.

5

Modified to this:

#include "Math.h"


double x;
double y;

void setup() {
Serial.begin(115200);
}

void loop() {

for (int i = 0; i < 144; i++){
  x = i;
Serial.println((asin((x-72)/72)+(PI/2))/PI);
delay(300);
}


}

An improvement, but still only seeing two decimal places on the output.

Still something about "i" being an integer?

6 
Serial.println((asin((x-72)/72)+(PI/2))/PI, 5);
8

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.