Hi,
Maybe this is just some detail in the syntax. The coordinate axes for the variable "temp" are not actually compressed, it's just that SHOW GRID is incorrectly saying they are. Are you seeing an error message? If this doesn't resolve things, please send more about the commands you are using and the results.
Your original example was with levitus_climatology, so let's go back to that.
yes? use levitus_climatology
yes? let test=TEMP-TEMP[X=@AVE,Y=@AVE]
yes? list test[x=@din,y=@din]
VARIABLE : TEMP-TEMP[X=@AVE,Y=@AVE]
FILENAME : levitus_climatology.cdf
FILEPATH : /home/users/tmap/ferret/linux/fer_dsets/data/
SUBSET : 20 points (DEPTH (m))
LONGITUDE: 20E to 20E(380) (XY integ.)
LATITUDE : 90S to 90N (XY integ.)
0 / 1: -538.5
10 / 2: -633.9
20 / 3: -530.8
30 / 4: -575.1
50 / 5: -335.4
75 / 6: -440.2
100 / 7: -459.0
150 / 8: -405.4
200 / 9: -287.2
300 / 10: -305.7
400 / 11: -234.4
600 / 12: -118.7
800 / 13: -113.0
1000 / 14: -73.9
1200 / 15: -52.0
1500 / 16: -35.0
2000 / 17: -6.6
3000 / 18: -13.9
4000 / 19: 7.7
5000 / 20: 0.5
On 12/3/2019 6:02 PM, Xiaoyu Bai wrote:
I picked the wrong word. I do want to remove the mean over lat and Lon. After that I want to apply @DIN. The compressed coordinates blocked @DIN to work. I tried with TEMP-Temp[x=@ave, y=@ave] and TEMP-number. They gave me very different results.
Thank you 😊
Xiaoyu
在 2019年12月3日，下午8:13，Ansley C. Manke <ansley.b.manke@xxxxxxxx> 写道：
Hi Xiaoyu,
First, what you have done with TEMP-TEMP[X=@AVE,Y=@AVE] is to remove the mean over longitude and latitude. That will not be less noisy. If you want to work with a less-noisy version of TEMP, you might use one of the smoothing transformations such as the boxcar smoother, @SBX. Here is a list of all the transformations:
https://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#Chapter3-Transformations, and further down that page are detailed descriptions of the different transformations.
Now, it looks as if you've discovered an error in the SHOW GRID output. It should not be listing the x and y axes as "compressed". So we'll look into that.
yes? use coads_climatology
yes? let sst_demean = sst - sst[x=@ave,y=@ave]
yes? show grid sst_demean
GRID GSQ1
name axis # pts start end subset
COADSX LONGITUDE 180mr 21E 19E(379) compressed
COADSY LATITUDE 90 r 89S 89N compressed
normal Z
TIME TIME 12mr 16-JAN 06:00 16-DEC 01:20 full
However sst_demean does still vary in longitude and latitude. See how STAT shows 180 points in X and 90 points in Y, and a plot at one time and latitude varies in X.
yes? stat/brief sst_demean
Total # of data points: 194400 (180*90*1*12*1*1)
# flagged as bad data: 89622
Minimum value: -23.622
Maximum value: 12.722
Mean value: -2.1127 (unweighted average)
yes? plot/L=1/y=0 sst_demean
First, what you have done with TEMP-TEMP[X=@AVE,Y=@AVE] is merely to remove the mean. If you want a less-noisy version of TEMP, you might look at the smoothing transformations. Here is a list of all the transformations:
On 12/3/2019 4:38 PM, Xiaoyu Bai wrote:
Dear ferreters,
I noticed that when I subtract area average from a variable, it will make the variable's Lat and Lon become compressed instead of full. For example:
use levi_climatologylet test=TEMP-TEMP[X=@AVE,Y=@AVE]
sh grid TEMP,test
GRID GMS1
name axis # pts start end subset
XAXLEVITR LONGITUDE 360mr 20.5E 19.5E(379.5) full
YAXLEVITR LATITUDE 180 r 89.5S 89.5N full
ZAXLEVITR DEPTH (m) 20 i- 0 5000 full
normal T
GRID GMS1
name axis # pts start end subset
XAXLEVITR LONGITUDE 360mr 20.5E 19.5E(379.5) compressed
YAXLEVITR LATITUDE 180 r 89.5S 89.5N compressed
ZAXLEVITR DEPTH (m) 20 i- 0 5000 full
normal T
What I want is to get a less noisy variable, then apply @DIN to it. But this compressed grid was blocking me to use @DIN.
So I am wondering how to get my coordinate to full again.
Thank you in advance.--
Xiaoyu