Logarithmic scale draw incorrect by plbox - 9 subticks instead of 10 by default. And params xtick and nxsub dont work - always 9 subticks. Using libplplotqtd.so
Alan W. Irwin
Note logarithmic scales have no zero so there are 9 ticks per decade corresponding to 2, 3, 4, 5,6,7,8,9,10, then the next decade is 20,...100, etc. See http://plplot.sourceforge.net/examples-data/demo04/x04.02.png for an example. There is absolutely no error in that log scale; it's the mathematical nature of logs. The same remarks apply to your attached plot. If you don't understand my remarks, then I suggest you read a tutorial about logarithms such as http://webmath.amherst.edu/qcenter/logarithms/index.html.
Also, you are absolutely right that the code ignores xtick and nxsub if the "l" opt parameter is used for plbox. Instead, the major tick marks are inserted every change of 1 in the log value, e.g., at 0.01, 0.1, 1., 10., 100., etc. I suppose you could make a feature request for skipping some of those, e.g, 0.01, 1., 100., 10000., but I don't think that would be a popular enough feature to justify the work. Currently, the minor tick marks are the 8 "integer" values between each decade value, e.g., 2,3,4,5,6,7,8,9 or 20,30,40,...90 so that is why nxsub is ignored. Again, I suppose you could make a feature request to have minor tick marks at different values, but again I don't think that would be a popular enough feature to justify the work.
I am closing this support request because I don't think there is much more to say.