Why is the Spatial Analyst toolbar graph different to Graphs>Create Graph?

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I'm using ArcGIS 10.3 and want to look at elevation vs frequency of each elevation for a DEM. There seems to be two ways to create this graph:

1. Use the "Create histogram" tool on the Spatial Analyst toolbar.
2. Go to View>Graphs>Create Graph.

The Histogram graph type in Create Graph looks very different to the Spatial Analyst one and I can't find a way to even set the x-axis field, so the graph doesn't work. The Vertical Bar graph type seems to be what I need but there are some differences that I don't understand. The graph created through the Spatial Analyst toolbar has a frequency count maximum of about 11,000. The Vertical Bar graph has a frequency count maximum of about 220,000. And although the general pattern of frequencies is the same, there are some differences - e.g. a couple of spikes are massive on the Vertical Bar graph compared the the Spatial Analyst histogram.

I can't find any ArcGIS documentation that explains this. Can anyone help?

Edit: By the way I am zoomed to the full extent of the DEM, so the Spatial Analyst histogram includes all pixels.



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