Re: [ferret_users] choosing a grid point

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Anup,
San Francisco is more like 122W, 37 N (not precisely - we'd need to look up the exact numbers) so if your grid is in units of longitude and latitude then you need to specify that.  These commands will show you information about the axes.

yes? show grid zo
yes? show axis `zo,return=xaxis`
yes? show axis `zo,return=yaxis`

Ferret uses I,J,K,L to refer to the index value, and X,Y,Z,T to refer to the coordinate in the units of the axis.  If you want to set a region based on indices, you can do that, but since they are indices they must be larger than 0.  This command would be ok:

      yes? set region/I=1/J=53

Or, if you use longitude/latitude values you would use decimal degrees, say /Y=37.21N  if that was the right number.

More commands to get familiar with the grid are these - they'll show the coordinate values along with the data values at those points:

yes? list/i=1:5/j=1/L=1 zo
yes? list/i=1/j=1:5/L=1 zo

yes? shade/L=1 zo  ! a 2D plot which will show you your x and y axes

Anup Sherchan wrote:

Hello ferret users
         I was just wondering if there is a way as to how I can choose a point so that I can do a harmonic analysis of sea-level.

I can choose the points using the following codes

/plot zo[i=17,j=48,l=1:8760]/
Here i=17,j=48 is the coordinate of California as I saw it in the plot using ncview (which works fine)
but when I use
/
set region/x=0W/y=53N
plot zo[l=1:8760]
/
which is the actual coordinates of San Francisco for which I have to plot the sea-level for, I get the following error
/
**ERROR: illegal limits: "ZO[L=1:8760]" is not in the range X=359
         Axis extremes are X=0.5:120.5
/

I would be very thankful if any of you could help me.

Anup Sherchan