====== What does "Bins must be in increasing order" mean ======
It can mean, that:
  * Your (self set) bins are really not in increasing order, or:
  * The number of bins does not correspond to the array you give the histogram to set the bins, for example, you have to set:
<code C>
double bins[5] = { 1,2,3,4,5 };
double nBins = 4;
TH1D* histo = new TH1D("histo","a histogram",4,bins);
</code>