View Full Version : logarithmic scale

1st July 2008, 10:43
hi all,

Could you, please, help me?
When I draw the bar-plot with logarithmic scale
scaleEngine = new QwtLog10ScaleEngine();

and I have Baseline = 0; (it shoud be drawn starting from the 0, i.e. from the infinity for logarithmic scale, i.e. from the bottom of the plot)

but values are drawn from the top, but not from the bottom of the plot...
e.g. I have yMax = 10.0
yMin = 1e-100

e.g. values: 12; 0.1; 0; -0.1; -12;

How can I do the following: The values equal 0 or less shouldn't be drawn at all, but values > 0 should be drawn from the bottom of the plot...

I am using qwt-5.0.2 and qt3.3

Thanks a lot!

1st July 2008, 14:55
log 0 or log (-n) - undetermined, and I don't see bars on the plot with this values.
but if "baseline" setted to "0", why bars (with positive value) are drawn from the top... :eek:

1st July 2008, 15:41
Okay, I think I know...
I'll just put baseline to minimum (yMin), and it's ok... :eek: