Malcolm Tang malct32 at gmail.com
Sun Dec 27 22:18:17 EST 2015

```Hi Andrew,

Exactly!

You have been of great help, Andrew.
Thanks and have a good day!

Regards,
Malcolm

On Fri, Dec 25, 2015 at 6:54 AM, Andrew Friedman <andfried at gmail.com> wrote:

> Hi Malcolm,
>
> I believe that what you are doing by plotting trendlast-trendl is
> comparing the fitted trend line at the last time step minus that of the
> first time step.
> I think that (trendlast-trendl)/ # of time steps should equal the slope.
> Is that what you find?
>
> Best, Andrew
>
> > On Dec 23, 2015, at 5:11 AM, Malcolm Tang <malct32 at gmail.com> wrote:
> >
> > Hi Andrew,
> >
> > Thanks for your guidance, it worked wonderfully.
> >
> > Just a quick question, though.
> >
> > 'sdfopen precipitation.nc'
> > 'set lon 0 360'
> > 'set lat -90 -75'
> > 'set mproj sps'
> > 'set t 1 last'
> >
> > 'd precipitation'
> > 'ltrend precipitation precl slope error'
> > 'c'
> >
> > 'set t 1'
> > 'd precl'
> > 'define trend1=precl'
> >
> > 'c'
> > 'set t last'
> > 'd precl'
> > 'define trendlast=precl'
> > 'c'
> >
> > 'd trendlast-trendl'
> >
> > *a spatial map comes out*
> >
> > Is this the correct way to display the fluctuation of precipitation
> trend?
> >
> > Regards,
> > Malcolm
> >
> > On Fri, Dec 18, 2015 at 4:59 AM, Andrew Friedman <andfried at gmail.com>
> wrote:
> > Hi Malcolm,
> >
> > If you are looking for the slope (the rate of change per time step) you
> need to add another term when you call trend
> >
> > For example:
> > 'ltrend prec precl precslope'
> >
> > >From the ltrend.gs”
> >
> > ga-> ltrend
> >   Calculate linear trend over time (based on least-squares fitting).
> >
> >   USAGE: ltrend <input> [<output> [<slope> [<rmse>]]]
> >     <input>: input field. Can be any GrADS expression.
> >     <output>: output field, i.e., fitted trend line. Default=<input>.
> >     <slope>: slope of fitted trend line, i.e., change of <input> per
> time step.
> >     <rmse>: root mean square error.
> >
> > Andrew
> >
> > > On Dec 17, 2015, at 1:28 PM, Malcolm Tang <malct32 at gmail.com> wrote:
> > >
> > > Hi Andrew,
> > > Yes I've set it as
> > >
> > > "set t 1 last"
> > >
> > > For your info, I tried this and a spatial map came out:
> > >
> > > 'set lon 0 360'
> > > 'set lat -90 -75'
> > > 'set mproj sps'
> > > 'set t 1 last'
> > >
> > > 'd prec'
> > >
> > > 'ltrend prec precl'
> > >
> > > 'd precl'
> > >
> > > I'm not sure if it's the spatial trend map that I'm looking for
> though....
> > >
> > > But since the time is set from 1 to last, I can observe that the map
> actually changes from 1 to the last time step.
> > >
> > > Any idea or suggestion?
> > >
> > > Thanks.
> > > Malcolm
> > >
> > >
> > > On Thu, Dec 17, 2015 at 5:32 PM, Andrew Friedman <andfried at gmail.com>
> wrote:
> > > Hi Malcolm,
> > >
> > > In your text earlier, it looks like your time is set to 1. Can you try
> setting time to varying?
> > >
> > > Andrew
> > >
> > > > On Dec 17, 2015, at 3:38 AM, Malcolm Tang <malct32 at gmail.com> wrote:
> > > >
> > > > Hi Andrew,
> > > >
> > > > I removed the bracket and ....... nothing came out?
> > > >
> > > > I typed:
> > > >
> > > > "ltrend prec fitted trend line" nothing came out.
> > > >
> > > > "ltrend prec fitted trend line 0.2 0.025" nothing came out.
> > > >
> > > > Should I be expecting a result or something? Because I'm expecting a
> spatial map to come up.
> > > >
> > > > Thanks!
> > > > Malcolm
> > > >
> > > > On Wed, Dec 16, 2015 at 4:05 PM, Andrew Friedman <andfried at gmail.com>
> wrote:
> > > > HI Malcolm,
> > > >
> > > > You shouldn’t type the brackets - they’re placeholders to indicate
> optional values.
> > > >
> > > > Andrew
> > > >
> > > > > On Dec 16, 2015, at 4:55 AM, Malcolm Tang <malct32 at gmail.com>
> wrote:
> > > > >
> > > > > Hi all,
> > > > >
> > > > > I want to plot the trend map of precipitation in antarctica
> (75s-90s) from 1999-2015.
> > > > >
> > > > > I have done some searching and saw someone suggested using
> BinGuan's script ltrend.gs
> > > > > I have copied the script and the dependencies qdims.gsf.
> > > > >
> > > > > So these are what I type in grads:
> > > > >
> > > > > 'set lon 0 360'
> > > > > 'set lat -90 -75'
> > > > > 'set mproj sps'
> > > > > 'set t 1'
> > > > >
> > > > > 'd prec'
> > > > > 'ltrend prec [fitted trend line [0.2[0.025]]]'
> > > > >
> > > > > and there will be error coming out: DEFINE error: Name too long;
> missing '='
> > > > >
> > > > > Anyone who has experience with ltrend.gs PLEASEEEEEEE help!!!
> > > > >
> > > > > Thanks
> > > > > Malcolm
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