[R] Fitting a line on trellis plot

[Michael Dewey]

On 25/03/2015 12:30, Frederic Ntirenganya wrote:
> Hi all,
>
> I am doing analysis which involves fitting a line on trellis plot.

But the commands below (or at least the output from them) are not 
plotting commands.

  The
> factor is month. As you know a year has 12 months and I expect to get
> 12 lines one for each month. I am getting the following results which
> is different to my expectation. Am I have to do anything about the
> data? Any suggestion is welcome. Thanks.
>
>
> Call:
> lm(formula = curr_data[[tmin_col]] ~ curr_data[[year_col]] -
>      1 | curr_data[[month_col]])

It would be simpler to say
lm(tmin_col ~ year_col - 1 | month_col, data = curr_data)

What did you think this was going to do? Is there any mention in the 
help for lm that you can use the | here?

It would also be helpful to see the result of str(curr_data) as we do 
not know what year_col is and we need to be sure that month_col is 
indeed a factor.

I am sure calendar experts on this list are readying themselves to 
question your assertion that all calendars have twelve months but that 
is rather off-topic.

>
> Residuals:
>      Min      1Q  Median      3Q     Max
> -5.0625 -0.7625  0.0375  0.9375  4.9375
>
> Coefficients: (1 not defined because of singularities)
>                                                         Estimate Std.
> Error t value Pr(>|t|)
> (Intercept)                                            15.56254
> 0.01079    1442   <2e-16 ***
> curr_data[[year_col]]  | curr_data[[month_col]]TRUE       NA
> NA      NA       NA
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>
> Residual standard error: 1.327 on 15115 degrees of freedom
>    (72 observations deleted due to missingness)
>
> Regards,
>
> Frederic.
>
>
> Frederic Ntirenganya
> Maseno University,
> African Maths Initiative,
> Kenya.
> Mobile:(+254)718492836
> Email: fredo at aims.ac.za
> https://sites.google.com/a/aims.ac.za/fredo/
>
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>
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-- 
Michael
http://www.dewey.myzen.co.uk