# Linear interpolator help

## Troubleshooting interpolator

The interpolator is implemented in JavaScript. If you do not have JavaScript enabled in your browser, the form will not work.

The x input values must be unique and the y values must be unique. This means the same number cannot appear twice in the x column or twice in the y column.

Exactly one box must be empty before clicking the Calculate button.

## Interpolation derivations

A straight line through (x_{1}, y_{1}) and (x_{2}, y_{2}) satisfies

To see why this is true, stick in x_{1} and x_{2} and see that you get y_{1} and y_{2}
out. If a linear fit is correct at two different points, it's correct
everywhere.

So if we set x equal to x_{3}, then

Solving for x_{3 }we see that

Back to the linear interpolator.

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