# 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

## Understanding data

Trying to make sense of data? We can help.