[R] Negative values on output

[John Kane]

It appears you posted in HTML and what we get is an almost useles set of data.  It is much better to supply it using dput() (and always post to the list in plain text not HTML.

See https://github.com/hadley/devtools/wiki/Reproducibility of http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example for some helpful hints on how to post to the R-Help list/


John Kane
Kingston ON Canada


> -----Original Message-----
> From: sam_l_cruickshank at hotmail.com
> Sent: Tue, 19 Aug 2014 19:09:13 +0100
> To: r-help at r-project.org
> Subject: [R] Negative values on output
> 
> 
> 
> 
> 
> 
> Good afternoon,
> I am completed a linear regression model which I personally am happy with
> the output and residual charts (although they are a bit bunched).  I have
> been using visreg() to visualise my data, and although I have logged the
> dependent variable (as it is cost data), on one of the graphical outputs
> I am getting negative fitted values for one of the Continents.  Attached
> is the data used, below is the code for the model and graph.  If anyone
> has any ideas I would hugely appreciate it, I tried a glm with log link
> too and this didn't help.
> LM22 <- lm(logTotal ~ logArea + Continent + factor(Method1) + Popdens,
> data=dummy)
> Output Residuals:     Min       1Q   Median       3Q      Max -1.22742
> -0.31675 -0.00909  0.28885  1.20224
> Coefficients:                       Estimate Std. Error t value Pr(>|t|)
> (Intercept)            -1.40972    0.77661  -1.815 0.081506 .  logArea
> 0.03811    0.04041   0.943 0.354619    ContinentAsia           3.51165
> 0.80009   4.389 0.000182 ***ContinentAustralasia    3.48549    0.97433
> 3.577 0.001454 ** ContinentEurope         2.44829    0.82369   2.972
> 0.006452 ** ContinentGlobal         2.37910    1.00668   2.363 0.026197 *
> ContinentNorth America  2.27953    0.62960   3.621 0.001303 **
> ContinentSouth America  3.60997    0.77627   4.650 9.22e-05
> ***factor(Method1)2        1.11259    0.38386   2.898 0.007696 **
> factor(Method1)3        0.82519    0.47470   1.738 0.094459 .
> factor(Method1)4       -0.06737    0.67341  -0.100 0.921104    Popdens
> -0.14261    0.31675  -0.450 0.656435    ---Signif. codes:  0 *** 0.001 **
> 0.01 * 0.05 . 0.1   1
> Residual standard error: 0.6151 on 25 degrees of freedom  (12
> observations deleted due to missingness)Multiple R-squared:  0.6998,
> Adjusted R-squared:  0.5677 F-statistic: 5.297 on 11 and 25 DF,  p-value:
> 0.0002714
> visreg(LM22) gives me a graph with "Africa" being within the realm of
> negative "Total" which is impossible.  If you tell me how  can provide
> the data and graphs, but the email was kicked back with them in.
> 	[[alternative HTML version deleted]]
> 
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