# PetroPlot Tutorial

# Pseudo Log Scale function

(This function is developed upon the suggestion of Dr. Yaoling Niu.)

Purpose:
In Excel log scale plots, the default minimum and maximum values on axes are fixed to the integer powers of 10th -- i.e., 0.001, 0.01, 0.1, 1, 10, 100, 1000 etc.
It is desirable that maximum and minimum on an axis can be of any values, e.g., 0.2, 0.6, 20, 40, 200 etc.
PetroPlot Pseudo Log Scale adds flexible log-scale labels on a linear-scale plot, so that the result looks like a log-scale plot.
It works for not only XY Scatter chart, but also line chart or bar chart etc.
Here is an example of XY Scatter chart with Pseudo Log Scale.
Here is an example of line chart with Pseudo Log Scale.

Start:
Calculate log10 values on worksheet.
Make linear scale chart using the log10 values. (For XY scatter chart, you can use the ChangeXY function)

Step 1:
Select the axis you want to label.
Click PetroPlot --> Pseudo Log Scale.

Step 2:
Type the log-scale labels.
The selected axis will be rescaled based on your input.
Click "O.K." button.
Notice the labels for Y axis are changed.

Repeat for each axis you want to add pseudo-log-scale.

Last modified 05/10/2002, Yong Jun Su
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