EZ Math Movie, Examples, Draw a function

The animating function

This example shows a common use of EZ Math Movie: Drawing and studying a function. Here we will see a parabola drawn and animated. The vertical scaling factor is varied during the animation, with the screen being cleared after the factor goes through one cycle. You can change the position of the parabola by clicking the '+' and '-' buttons on the horizontal and vertical translation input gizmos.

Press the 'Go' button, which looks like this: , to get things started.

// Initialize vertical scaling factor.
a = 0.1;

// Change in vertical scaling factor.
deltaA = 0.01;

// Vertical scaling factor domain.
aMin = -2;
aMax =  2;

// Change in x-coordinate.
deltaX = 0.5;

// Clear and prepare graph.
setupGraph();

// Get horizontal translation.
h = get1stInputValue();

// Get vertical translation.
k = get2ndInputValue();

// Get first function point.
x1 = worldXMin;
y1 = a * (x1-h)*(x1-h) + k;

// Sweep across x-axis.
for(x2 = worldXMin; x2 <= worldXMax; x2 += deltaX)
{
  // Get y-coordinate.
  y2 = a * (x2-h)*(x2-h) + k;
  
  // Draw.
  drawPoint(x1, y1);
  drawLineSegment(x1, y1, x2, y2);
  
  // Second point becomes first point.
  x1 = x2;
  y1 = y2;
}

// Change vertical scaling factor.
a += deltaA;

// Is vertical scaling factor past the maximum?
if(a > aMax)
{
  // Yes, set it to the maximum.
  a = aMax;

  // Reverse the change.
  deltaA = -deltaA;
}

// Is vertical scaling factor past the minimum?
if(a < aMin)
{
  // Yes, set it to the minumum.
  a = aMin;
  
  // Reverse the change.
  deltaA = -deltaA;
}

// Show the vertical scaling factor.
set1stOutputValue(a);

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EZ Math Movie, Examples, Draw a function

The animating function

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