Re: [ferret_users] Ferret equivalent to Matlab "axis equal"

["William S. Kessler" <william.s.kessler@xxxxxxxx>]

Here's a code snippet that defines the aspect for a window to plot a  
map with the correct ratio (taking into account the changing distance  
of a degree longitude). Call it with the 4 arguments for the  
west,east,south,north edges of your map.

You might want to edit horfrac, vertfrac, xstart, ystart, or make them  
arguments.

define symbol west `$1`;define symbol east `$2`;define symbol south  
`($3)`;define symbol north `($4)`
def sym emw `($east)-($west)`
def sym nms `($north)-($south)`
def sym avlat `(($north)+($south))/2`
def sym scale_emw `cos(pi*($avlat)/180)*($emw)`
def sym horfrac 1.3; def sym vertfrac 1.4         ! size of window  
relative to the plot box
let hor=`($scale_emw)*($horfrac)`; let vert=`($nms)*($vertfrac)`
set win/asp=`vert/hor`
def sym xstart `0.11`; def sym ystart `0.12`     ! fractional distance  
to the left/bottom edge of the plot box
def vi/axes/xli=($xstart),`($xstart)+1/($horfrac)`/ 
yli=($ystart),`($ystart)+1/($vertfrac)` glvi
set vi glvi

... now plot your map ...


On Jul 25, 2013, at 11:52 , Daiwei (David) Wang wrote:

> Hi Ferreters,
>
> I wonder if there is an easy way to "set the aspect ratio [of a  
> viewport] so that the data units are the same in every direction" as  
> with "axis equal" in Matlab [1]. In other words, for example, I'd  
> like 1-degree-by-1-degree boxes shown as squares, not rectangles, in  
> a shade plot.
>
> Thanks,
> David
>
> [1] http://www.mathworks.com/help/matlab/ref/axis.html