How do I get the slope of a waveform chart?

[Capillod]

I am reading in a Voltage into a Waveform chart and i want to get the slope of the chart.
The voltage is decaying at a log scale. I want the slope to make caculations.
I have tried using Linear Fit.vi and other vi's of this nature but with no success.

See attachment for my program.

[Capillod]

This is a version of the Linear Fit.vi i got online and tried to use with my program vith no success.

[Kaustubh_vc]

Hi!
See the attachment.
Hope so this will work for you.

KAustubh
VC (Pune)
INDIA