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--- root:setaxisrange [2010/11/09 16:08] – created nchiap
+++ root:setaxisrange [2014/03/11 10:20] (current) – [X Axis of TGraph] add missing call to GetXaxis nchiap
@@ Line 1: / Line 1: @@
 ====== Set Display Range of Axis ======
+The normal way to change the display range of an axis is:
 <code C++>
 histogram->GetYaxis()->SetRangeUser(lower,upper);
 </code>
+but there are several situations where this fails. See below for help in these cases.
+===== Y Axis of a normalized Histogram =====
+Assume you have a histogram which has been normalized it with
+<code c++>
+hist->SetNormFactor(1)
+</code>
+Your Y-axis will show values between 0 and 1.
+Trying to set the Y range using these values, eg.
+<code c++>SetRangeUser(0.01, 0.2)</code>
+will fail however.
+You still need to give the range in the original unnormalized units.
+You can scale normalized units back with:
+<code C++>
+Double_t scaleY = hist->GetEntries()/hist->GetNormFactor();
+hist->GetYaxis()->SetRangeUser(normalizedLower*scaleY,normalizedUppe*scaleY);
+</code>
+===== Y Axis of a THStack =====
+Do not try to ''SetLimits'' or ''SetRangeUser'' of any histogram.
+Instead use the following code:
+<code c++>
+THStack *hs = new THStack("hs","test stacked histograms");
+hs->SetMinimum(0.);
+hs->SetMaximum(10.);
+</code>
 ===== X Axis of TGraph =====
@@ Line 12: / Line 42: @@
 TGraph* myGraph = new TGraph();
 ...
-myGraph->SetLimits(lower,upper);
+myGraph->GetXaxis()->SetLimits(lower,upper);
 </code>

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