# How to plot Ixt with monologarithmic scale and find linear fit

1. Apr 14, 2012

### carlosbgois

I have some experimental data of a simple RC circuit, which I measured in fixed time intervals the current through an microamperimeter, and now I need to make an $i(t) × t$ graph, with the vertical axis on a logarithmic scale (so my points fall into a 'straight' line), and then I need to find the linear fit for that.

Until now I was using Origin for creating all graphs I needed, but I only know the real basic stuff, and couldn't find my way on solving this particular problem. I also have Mathematica and MATLAB available, so if you do not know how to do that on Origin but know on any other software, it would also be helpful.

Thanks

2. Apr 14, 2012

### gsal

Hhhmmm...I think you are making matters more confusing by attempting to fit a "straight line" of numbers you have taken the log of...

...if you KNOW that your points follow exponential behavior, you should propose the form of the equation that should generate your points, then, determine the constants in such equation as to minimize the error with your data points (least squares).

does this make sense? or did I totally misunderstood your problem?

3. Apr 15, 2012

### carlosbgois

Thanks for your answer. I may not have been very clear, but I did not take the log of my number, I just need to plot the raw data in an logarithmic scale (only on the y axis), and then find the linear fit and plot also using that scale.

Your other alternative is also considerable, because I do have the exponential form for which my points theoretically corresponds. But either this way, I have no idea of how to do it.

4. Apr 15, 2012

### gsal

Here are a couple of links, hope they help.

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