# [Chimera-users] electron density ven diagram

Terry Lang terry at lego.berkeley.edu
Mon Apr 23 09:28:34 PDT 2012

```Hey Guys,

I am interested in making kind of a ven diagram between two
maps for electron density (see attached).  What I would like to do is
where the density is above a certain threshold for both maps, color the
map grey, and where it is above the threshold for map A only, color red,
and for map B only, blue.

Plan #1
--superimpose maps (have this working)
--create a third map (have this working)
--do a direct < > = point-by-point comparison between map A and B and
reset the values of the third map to be -1 (map A only), 0 (both maps)
or 1 (map B only)
--color the map using the histograms
PROBLEM:  The maps are not gridded the same.  After some careful
thought, I don't think I actually can get them gridded the same for
technical reasons.

Plan #2
--superimpose maps (have this working)
--create copy of map A (coarser map) with map A gridding (have this working)
--use interpolation function to interpolate map B (finer map) onto map A
gridding
--create copy of map A and do a direct < > = point-by-point comparison
between map A and interpolated map B and reset the values of the fourth
map to be -1 (map A only), 0 (both maps) or 1 (map B only)
--color the map using the histograms
QUESTION:  Is there an easier way to do this with tools that already
exist in Chimera?  If not, can I get a little bit of info on how the
data is stored in the ccp4 style maps (eg start at origin and loop over
x, loop over y, loop over z or something else?)

Let me know if you need more details or clarification on this rats nest.

Thanks!
Terry

--
Paula Therese Lang
Postdoctoral Scholar
Alber Lab
UC Berkeley/QB3

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