Hi Surendra, The vop (volume operation) command can subtract two maps. For example vop #0 subtract map #1 creates a new map that is the difference between maps 0 and 1. The original maps must have identical grids. If they don't have identical grids then you can use the vop "resample" and "onGrid" options to interpolate one map the others grids. You may need to scale one of your maps before subtracting. There is no vop option to do a simple scaling yet. You can do it with a Chimera 1.4 daily build with the Tools / Volume Data / Volume Filter dialog using the Scale filter. To figure out a scale factor one approach is to equalize enclosed volume. You could use the Measure Volume and Area dialog (Tools / Volume Data) to achieve that. Tom Eric Pettersen wrote:

On Apr 9, 2009, at 9:23 AM, Negi, Surendra S. wrote:

...

Hi Eric,

I have a quick question related to chimera. Can we use chimera to calculate the difference map between two EM densities.

Hi Surendra, I don't know the answer to this off the top of my head, so I'm cc'ing this to chimera-users, where someone who does know the answer can reply.

--Eric

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