[Chimera-users] chimera difference map

Thomas Goddard goddard at cgl.ucsf.edu
Thu Apr 9 10:55:35 PDT 2009

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.


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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