Slope equation calculation (Is it the same as trendline?)

Hi there, I'm trying to calibrate a temperature monitoring system in reference to a calibrated one. The relation is not linear, so the difference equation is not linear. This is where Excel com...

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HansVogelaar
Mar 19, 2025
The forum has been broken since late 2024. I only now got a notification of your reply.

For a 4th degree polynomial, you can't just calculate the slope - you have to calculate the coefficients for x, x^2, x^3 and x^4. For OpSens CH2 to PICO CH1:

To use this to predict/interpolate values:

These values look reasonable to me.

theDeCoder01

Copper Contributor

Mar 18, 2025

Hey Hans,

Thank you for your input!

IDK what happened to my first reply. However, attached is one sheet of my workbook with JKPieterse's idea in the first graph.

Thanks!

HansVogelaar

MVP

Mar 19, 2025

The forum has been broken since late 2024. I only now got a notification of your reply.

For a 4th degree polynomial, you can't just calculate the slope - you have to calculate the coefficients for x, x^2, x^3 and x^4. For OpSens CH2 to PICO CH1:

To use this to predict/interpolate values:

These values look reasonable to me.

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Slope equation calculation (Is it the same as trendline?)