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Re: [ferret_users] Append one time step

Hi Sam,
It sounds as if you've defined the grid you want, and defined a variable which is the original variable on your new grid.

The thing to do next is to define expressions to do the operation on the variables/grids. Here's a variable with the data shifted so that the data that was at timestep 52 will be in timestep 53:

   let varshift = newvar[L=@shf:-1]

This variable keeps what was in the original variable for 52 timesteps, and uses the shifted data in that last timestep.

   let var_final = if L LE 52 then newvar else varshift

(By the way, this isn' really "appending" here, in the sense that we append when writing out data to a file. Instead it's defining a variable that has the desired grid and data once some or all of it is loaded into memory.)


On 4/7/2015 11:40 AM, Sam Rabin wrote:
[Sorry if this double-posts; I think I used the wrong email address before.]

All —

I have a 3-D variable whose time axis is irregular (January 1 of each year: 1500, 1600, 1700:1980:10, 1990:2010:1). I would like to simply copy the values for each grid cell in 2010 and set that as the value for some arbitrary future date (e.g., 2011). Of course, nothing is ever so simple.

I’ve already managed to create a new grid (GMH1), based on the old grid (GRS1), that has an extra (empty) time step at 01-JAN-2011 00:00. What I’m having trouble with now is saving the L=52 value as L=53. How would I do this?

Relevant info (?):

 name       axis              # pts   start                end
 LON       LONGITUDE          720mr   179.75W(-179.75)     179.75E
 LAT       LATITUDE           360 r   89.75S               89.75N
 normal    Z
 TIME1     TIME                52 i   01-JAN-1500 00:00    01-JAN-2010 00:00

 name       axis              # pts   start                end
 LON       LONGITUDE          720mr   179.75W(-179.75)     179.75E
 LAT       LATITUDE           360 r   89.75S               89.75N
 normal    Z
 TIME2     TIME                53 i   01-JAN-1500 00:00    01-JAN-2011 00:00

And here are the last four lines of LIST NEWVAR[I=@SUM,J=@SUM), to show that the last (new) point is indeed empty:

 JAN-2008 / 50:  3580402.
 JAN-2009 / 51:  3622055.
 JAN-2010 / 52:  3663709.
 JAN-2011 / 53:      ....
Thanks in advance.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Sam Rabin
PhD student, Ecology & Evolutionary Biology
Princeton University 

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