[R] Trend value from smoothing spline trend fit

[Dileepkumar R]

Dear Bert Gunter and Mathew Guilfoyle,

Thanks for the reply.

I also agree with you. But that is the actual slope of the straight line
connecting from the first estimated value to last estimated value ( like
dy/dx slope). I tried in that way also, but I couldn't replicate the
results as given in that  Box 2.2, Table 1 and Figure 1.  I can replicate
the line plot as in Box 2.2,  Figure 1 (a) (to verify my input data is the
same as in Figure 1 (a)).

You can see my plot here:
https://drive.google.com/file/d/14WDFFW5J69WvxnhbfdcOZKvGRk6HUWVn/view?usp=sharing


I have attached my code and data (as NetCDF file) along with this mail.

input Data (only 32Kb) :
https://drive.google.com/file/d/1Wt5sjVhWmjhRWOfdc6elUzwOvifRk-OI/view?usp=sharing

code:
https://drive.google.com/file/d/1r5mg1vcNmDCIf19jnMUAFEiLNOLKQiKq/view?usp=sharing

output figure:
https://drive.google.com/file/d/1bEXWCB-H5doVKXO8i_FLO7KZMW3qc9Cw/view?usp=sharing

Sincerely,

Dileepkumar R



On Tue, Aug 11, 2020 at 11:41 PM Mathew Guilfoyle <mrguilfoyle using gmail.com>
wrote:

> Looking at the report (specifically the legend for the table) I think all
> they have done is take the difference between fitted temperatures (given by
> linear regression or the GAM) at the start and end of each period (e.g. in
> 1901 and 2012), and then calculate the average change per year.
>
> In a way it ‘linearises’ the spline trend but I don’t think it’s really
> valid.  It just highlights how poorly a (simple) linear regression can fit
> a very non-linear trend.
>
> > On 11 Aug 2020, at 13:21, Dileepkumar R <dileepkunjaai using gmail.com> wrote:
> >
> > Dear All,
> >
> > I am trying to estimate the non -linear trend value from smooth spline
> > trend fit (using the generalized additive model (GAM)).
> >
> > I want to estimate the trend value from a temperature dataset (spatial
> > averaged annual meantime from 1906 to 2005) as given in the Box 2.2,
> Table
> > 1  in the attached Google doc pdf.  (That pages are from  IPCC Assessment
> > Report 5 chapter 2
> > <
> https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_Chapter02_FINAL.pdf
> >,
> > page number 21-22 )
> >
> > I do not understand how they estimate the single value trend with 95%
> > confidence interval from a time-series data as given in the Box 2.2,
> Figure
> > 1.  Is there any easy way to extract the trend value using mgcv library
> of
> > R.?
> >
> > Google Doc Link:
> >
> https://drive.google.com/file/d/1z3XLW-154dsZE6GrvQ4rH_fev9lqdsho/view?usp=sharing
> >
> > Thank you all in advance
> >
> > Dileepkumar R
> >
> >    [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]