Pentaho: logarithmic scale in charts

Question

Is there a way to set a "logarithmic scale" in a Pentaho chart? Result from my sql query has a very wide range (from 1 to 1000000).

I could change my sql query to something like this:

"Select LOG(10, wide_value)..."

But Y-axis scale changes the same way at Pentaho chart (1,2,3...). I need the original labels on Pentaho chart (10,100,1000...).

What I found on web are old forums talking about that this is still a feature request, or to try with "CCC" (too much documentation for something too simple) or to modify the source code (even worse). None of them useful.

Hint: I'm using a legacy implementation on Pentaho bi-server 6.0. If there is an option on newer versions it will be useful too, maybe there is something similar on my old version.

cesargastonec cesargastonec · Accepted Answer · 2019-08-13T03:44:11

This is the solution in case someone else needs it. My query originally delivered something like:

Select
   x_axis as "x_axis",
   y_axis_wide_value as "value"
From ...

It must be modified to:

Select
    x_axis as "x_axis",
    LOG(10, y_axis_wide_value) as "value"
From ...

My graphic in Pentaho's "Components Panel" is a "CCC Line Chart".

What I needed is for the Y axis to show the real values. That is achieved as follows: In "Advanced Properties" you must locate "OrthoAxisThickFormatter" and enter the following function:

function fun (value)
{
     return Math.pow (10, value);
}

Some additional settings for better viewing:

orthoAxisOriginIsZero: false
orthoAxisZeroLine: false

And that was all. Now my graphs are displayed with logarithmic scale.

Pentaho: logarithmic scale in charts

1 Answers