What this page adds. The
basic calculator draws straight lines between
your points and never leaves your browser. This page fits curves instead —
cubic spline, PCHIP, and Akima — and takes any number of series at once.
To do that it sends your table to the server, computes there,
and sends the numbers back. Nothing is stored, but the data does leave your
machine. If that matters for your data, use the basic page.
The interpolation article explains what each
method assumes and where each one goes wrong.
- Paste your data into the Input grid — straight from a
spreadsheet, or as CSV/TSV text. First column is x, every other column is
a y series. There is no column limit on this page.
- Or press import to load a file instead. CSV and TSV both
work — the separator is detected from the file, so a comma file and a tab
file of the same numbers give the same grid. The file is read in your
browser and is not sent anywhere.
- Set the output range. Output X start, finish, and interval
decide which x values you get back.
- Real time range — try settings live on the three range boxes.
- ▲▼ buttons or the mouse wheel over a
box: the value moves and the result is recomputed shortly after the last
step - one request to the server, not one per step.
- Digit wheel: over a box, the wheel steps the digit just
left of the mouse pointer.
- Limits: the interval stays above 0; a typed value below
it is set to the limit. Start and finish follow your data.
- Typing or the arrow keys change the box only; press
interpolate to recompute.
- Pick a method in the Method select, then press
interpolate.
- Read the result. Values land in the Output grid; the same
curves plot under Results.
- Press export to save the Output grid as a file. The save
dialog offers CSV or TSV and whichever you choose decides the separator.
On Firefox and Safari the browser cannot offer that choice, so a small
CSV/TSV menu appears next to the button instead. Saving happens in your
browser; only interpolate talks to the server.
Output x values outside the range of your data are left blank. This
interpolates between your points, it does not extrapolate past them.