Hi Geoffrey,

Yes, it would save time to multiply the projection object by a constant factor if your projection has already been done. However, it is a bit dangerous to do this since now you need to manually edit how all the units/labels work out.

I'd suggest just creating a new derived field that uses the convert_function option (http://yt-project.org/docs/dev/analyzing/creating_derived_fields.html#field-options). A good, non-trivial example is the SZY field:

https://bitbucket.org/yt_analysis/yt/src/61e6b84f875cc8fcf25b5b1e67ddd501a19daf68/yt/data_objects/universal_fields.py?at=yt#cl-577

If you do want to manually modify an projection object, you can do something like the following:

from yt.mods import *

pf = load('IsolatedGalaxy/galaxy0030/galaxy0030')

proj_pw = ProjectionPlot(pf, 0, 'Density', weight_field='Density')

proj_pw.save('before')

proj_pw.data_source['Density'] *= 1.5

proj_pw.refresh()

proj_pw.save('after')

Sam

On Mon, Feb 24, 2014 at 12:26 PM, Geoffrey So <gsiisg@gmail.com> wrote:

Hi all,

Will I be saving computation time by multiplying some constant conversion factors on the projection object instead of creating a derived field with an existing field multiplied by the factors?

And how would I go about multiplying the projection by some factors?

If there's no significant saving I'll just do the derived field.

From

G.S.

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