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Base 2 Log Plot in Excel - How?
4

Base 2 Log Plot in Excel - How?

Base 2 Log Plot in Excel - How?

(OP)
I'd like to plot some data on a semilog plot but in excel the default for log plots is base 10 (i.e. 1,10,100 etc).  Is it possible to setup a plot such that the x-axis is base 2, and starts at 125 (i.e. 125,250,500 etc)?

(Reason is - I'm trying to plot some noise data on a dB vs. Octave graph, with Frequencies between 125 and 8K Hz)

Thanks.

RE: Base 2 Log Plot in Excel - How?

One way to set it up is to compute the log2 of the numbers, and plot that on the figure. For instance, instead of using the log option on the x-axis (which you know plots log10 on the axis), you could compute the log10 of the x-values, and plot those log10 values. Instead of the x-axis being "1,10, 100, etc." your x-axis would be "1,2,3, etc.". An analogous procedure could be used with log2 of the x-axis. Or y-axis. If you are worried about the labeling, you could always use a text box in Excel, paste it over the top of the labels.

RE: Base 2 Log Plot in Excel - How?

4
Via Jon Peltier, arguably the guru for Excel Charts (http://peltiertech.com/Excel/Charts/ArbitraryAxis.html) I got to Tushar Meta's excellent site, which contains a lot of amazing Excel tips and tricks: http://www.tushar-mehta.com/excel/newsgroups/flexible_log_scale/index.html
The workaround basically adds another data series which takes the place of the X-axis (or Y-axis, the principle is the same). This works a little bit better than a superimposed text box.

Cheers,
Joerd

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RE: Base 2 Log Plot in Excel - How?

well i think that's worth a star ...

RE: Base 2 Log Plot in Excel - How?

Thanks

Cheers,
Joerd

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Base 2 Log Plot in Excel - How?

(OP)
thanks, that method works.  

RE: Base 2 Log Plot in Excel - How?

(OP)
Update:
Sorry to bring this up from the dead but (un)fortunately I was recently upgraded to Office 07 and found out that Excel now has a built-in option to change the "base" of the log plot.  It works quite well.

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