# [Numpy-discussion] [JOB] Extracting subset of dataset using latitude and longitude

Chao YUE chaoyuejoy@gmail....
Fri Jan 13 16:31:58 CST 2012

```Hi, I don't know if numpy has ready tool for this.
I also have this use in my study.  So I write a simple code for my personal
use. It might no be great. I hope others can also respond as this is very
basic function in earth data analysis.

############################################################3
import numpy as np
lat=np.arange(89.75,-90,-0.5)
lon=np.arange(-179.75,180,0.5)
lon0,lat0=np.meshgrid(lon,lat)  #crate the grid from demonstration

def Get_GridValue(data,(vlat1,vlat2),(vlon1,vlon2)):
index_lat=np.nonzero((lat[:]>=vlat1)&(lat[:]<=vlat2))[0]
index_lon=np.nonzero((lon[:]>=vlon1)&(lon[:]<=vlon2))[0]

target=data[...,index_lat[0]:index_lat[-1]+1,index_lon[0]:index_lon[-1]+1]
return target

Get_GridValue(lat0,(40,45),(-30,-25))
Get_GridValue(lon0,(40,45),(-30,-25))
############################################################

Chao

2012/1/13 Jeremy Lounds <jlounds@dynamiteinc.com>

> Hello,
>
> I am looking for some help extracting a subset of data from a large
> dataset. The data is being read from a wgrib2 (World Meterological
> Organization standard gridded data) using the pygrib library.
>
> The data values, latitudes and longitudes are in separate lists (arrays?),
> and I would like a regional subset.
>
> The budget is not very large, but I am hoping that this is pretty simple
> job. I am just way too green at Python / numpy to know how to proceed, or
> even what to search for on Google.
>
> If interested, please e-mail jlounds@dynamiteinc.com
>
> Thank you!
>
> Jeremy Lounds
> DynamiteInc.com
> 1-877-762-7723, ext 711
> Fax: 877-202-3014
> _______________________________________________
> NumPy-Discussion mailing list
> NumPy-Discussion@scipy.org
> http://mail.scipy.org/mailman/listinfo/numpy-discussion
>

--
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Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
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