matplotlib-users

[Matplotlib-users] Basemap Mercator y-axis latitude ticks

[Michael B. <mb...@jp...>]

When using Basemap with a Mercator projection, is there a simple way to 
tell the Axes to label the y-axis ticks in latitude degrees instead of 
native map coord meters?

Here's the way I did it.  I created my own Formatter:


class MercYAxisFormatter( matplotlib.ticker.Formatter ):
    """The format function for Mercator projection Y-axis.
    Translates plot y in meters to latitude.
    """

    def __init__( self, baseMap ):
       self.baseMap = baseMap

    def __call__( self, y, pos=1 ):
       """Return the label for tick value y at position pos.
       """

       lon, lat = self.baseMap( 0.0, y, inverse=True )
       return "%.0f" % lat


and added it like so:

   baseMap = Basemap( ... )
   ax.yaxis.set_major_formatter( MercYAxisFormatter( baseMap ) )


This works just fine, but is there a simple one-liner in Basemap that I'm 
missing that does this?

Thanks,

Michael

-- 
========================================================================
  Michael Brady
  Jet Propulsion Laboratory (M/S 301-140L)
  4800 Oak Grove Drive
  Pasadena, CA  91109                 E-mail: Michael.Brady@...
========================================================================

Re: [Matplotlib-users] Basemap Mercator y-axis latitude ticks

[Jeff W. <js...@fa...>]

Michael Brady wrote:

> When using Basemap with a Mercator projection, is there a simple way 
> to tell the Axes to label the y-axis ticks in latitude degrees instead 
> of native map coord meters?
>
> Here's the way I did it.  I created my own Formatter:
>
>
> class MercYAxisFormatter( matplotlib.ticker.Formatter ):
>    """The format function for Mercator projection Y-axis.
>    Translates plot y in meters to latitude.
>    """
>
>    def __init__( self, baseMap ):
>       self.baseMap = baseMap
>
>    def __call__( self, y, pos=1 ):
>       """Return the label for tick value y at position pos.
>       """
>
>       lon, lat = self.baseMap( 0.0, y, inverse=True )
>       return "%.0f" % lat
>
>
> and added it like so:
>
>   baseMap = Basemap( ... )
>   ax.yaxis.set_major_formatter( MercYAxisFormatter( baseMap ) )
>
>
> This works just fine, but is there a simple one-liner in Basemap that 
> I'm missing that does this?
>
> Thanks,
>
> Michael
>
Michael:  No, you're not missing anything - the functionality of basemap 
is rather basic at this point.  Thanks for the tip though!

-Jeff

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