The Histogram tool on the Spatial Analyst toolbar displays values for the entire dataset, not just the clipped portion.
The display of values for the clipped portion of a raster in the histogram is not supported; thus, all values for the entire dataset will be displayed in the histogram.
Solution or Workaround
Don't use the Clip To Shape option of the Data Frame properties.
To view a histogram for a portion of a raster:
- Draw a graphic element over the portion of the raster of interest.
- Make sure the graphic element is still selected, then click the Histogram tool on the Spatial Analyst toolbar.
The histogram will only display the number of values underneath the graphic.