Hi,
While it's a nice fantasy to offer users the ability to type in
arbitrary expressions for server-side processing, in practice it's
much more difficult than we first imagined. First of all are many,
many things about the Ferret syntax that are also significant to the
URL syntax and no amount of encoding can remove the way they are
interpreted by web servers and web clients. Secondly, we quickly
discovered that if every newly created variable used as part of a
calculation to create a complex expression is exposed in the final
data set, the final data set is a mess.
To alleviate the second problem we made the arbitrary decision that
only virtual variables that belong to the first data set "/d=1" in
Ferret notation will be exposed in the final F-TDS data set. And to
alleviate the second problem that let/d=1 a=sst*2 requires a "/" that
is significant to the URL syntax we created an alias that is always
active for virtual variable created with _expr_ expressions. letdeq1
can be used in place of let/d=1.
So your analysis URL should look like this:
data_coads_climatology.jnl_expr_{}{letdeq1%20A=SST*2}.ascii?A
No doubt our documentation is out of date and we'll get to work on
fixing it.
Roland
On 09/15/2011 11:37 PM, Wang Jiqin wrote:
Hi,
We followed the exact step to install and config F-TDS with LAS.
Ferret version: 6.72
Las version: 7.3 (tested on 7.2 too)
OS: RHEL 6
Tomcat Version: 6.0.32
We are able to view
http://IP:8080/thredds/dodsC/las/coads_climatology_cdf/data_coads_climatology.jnl.ascii?SST[0:1:1][0:1:5][0:1:5
<http://IP:8080/thredds/dodsC/las/coads_climatology_cdf/data_coads_climatology.jnl.ascii?SST%5b0:1:1%5d%5b0:1:5%5d%5b0:1:5>]
this is working fine, we can see the values in ascii
However, when doing server data analysis, it returns error.
http://IP:8080/thredds/dodsC/las/coads_climatology_cdf/data_coads_climatology.jnl_expr_%7B%7D%7Blet%20A=SST*2%7D.ascii?A
Error {
code = 2;
message = "The variable `A' was not found in the dataset.";
};
Debug logs of ferretIOSP
[...]
I have attached the details logs in the zip file attached.
Please help and thanks in advance.
Regards,
Jiqin