Simplify if then else statements for Neopixel/compass project
You don't use the correct syntax. I assume you mean:

// NeoPixel Display   
if ((counter &gt;=3) &amp;&amp; (counter &lt;=9))
{
  strip.setPixelColor(0, 255, 0, 0); //set pixel number 1 and set color to red
  strip.show(); //send color to pixel 1 on NeoPixel Ring  
}
else 
{
  strip.setPixelColor(0, 0, 0, 0)
  strip.show();
}


And similar for the other colors.

First you see there are a lot of occurences of calls to setPixelColor and show. We make a function of this, where the color and the red value is parameterized:

void setPixel(int pixelNumber, int red)
{
  strip.setPixelColor(pixelNumber, red, 0, 0);
}


Now we can write your code as

// NeoPixel Display   
if ((counter &gt;=3) &amp;&amp; (counter &lt;=9))
{
  setPixel(0, 255);
}
else
{
  setPixel(0, 0);
}

void setPixel(int pixelNumber, int red)
{
  strip.setPixelColor(pixelNumber, red, 0, 0);
  strip.show();
}


And similar for the other colors.

Now we get rid of the if statements. For the first color this will become:

// NeoPixel Display   
setPixel(0, ((counter &gt;= 3) &amp;&amp; (counter &lt;= 9)) ? 255 : 0);


Combined with the other colors we get

// NeoPixel Display   
setPixel(0, ((counter &gt;=  3) &amp;&amp; (counter &lt;=  9)) ? 255 : 0);
setPixel(1, ((counter &gt;= 10) &amp;&amp; (counter &lt;= 15)) ? 255 : 0);
setPixel(2, ((counter &gt;= 16) &amp;&amp; (counter &lt;= 21)) ? 255 : 0);

void setPixel(int pixelNumber, int red)
{
  strip.setPixelColor(pixelNumber, red, 0, 0);
  strip.show();
}


However, the conditions can be simplified by adding them into the function. So we get

// NeoPixel Display   
setPixel(0, counter,  3,  9);
setPixel(1, counter, 10, 15);
setPixel(2, counter, 16, 21);

void setPixel(int pixelNumber, int counter, int lowValue, int highValue)
{
  strip.setPixelColor(pixelNumber, 
     ((counter &gt;= lowValue) &amp;&amp; (counter &lt;= highValue)) ? 255 : 0, 
     0, 0);
  strip.show();
}


If you need to have more checks if a value is in range you can make it a specific function. This will increase the code, but makes it easier to reuse code. So you will get:

// NeoPixel Display   
setPixel(0, counter,  3,  9);
setPixel(1, counter, 10, 15);
setPixel(2, counter, 16, 21);

void setPixel(int pixelNumber, int counter, int lowValue, int highValue)
{
  strip.setPixelColor(pixelNumber, 
    inRange(counter, lowValue, highValue) ? 255 : 0,
     0, 0);
  strip.show();
}

int inRange(int counter, int lowValue, int highValue)
{
   return ((counter &gt;= lowValue) &amp;&amp; (counter &lt;= highValue));
}