missing data in plot

Dear All,
I'm using matplotlib to generate graph from measured data in one of our
accelerators. The issue I have, that the data vector is huge. We talk,
say about 50000 points to be displayed in a single graph, and I have to
assure, that those points are really there. Otherwise the image will be

Now, I did a plot like this one:


The top-picture is somehow still correct, however bottom picture, which
should display data on the sample x-axis places as top one, is evidently
broken. The problem was traced somewhere into matplotlib, because the
original data used to construct the graph are fine.

Moreover, if I plot the same data, but just require different x-axis
setting to 'zoom' on a part, e.g. 350-600 of the original image linked
above, I get correct data output:


This leads me to a conclusion, that matplotlib somehow 'chooses' the
data to be displayed.

How can I force it to display all the data? I do not mind if not all the
data are displayed in the graph, but it seems that it does not bother to
skip as well the peaks, which are of utmost importance...

any help appreciated.

The source code to display the graphs is shown in function
writePdfBSlots in following code:


thanks for any help