[R] Interpreting Multiple Linear Regression Summary
John C Frain
frainj at gmail.com
Wed Nov 9 20:32:50 CET 2011
As far as I know if there is an NA in any variable in an observation
the default is to drop the entire observation. Thus there are no
observations in your calculation
Best Regards
John
On 9 November 2011 19:17, Rich Shepard <rshepard at appl-ecosys.com> wrote:
> On Wed, 9 Nov 2011, Daniel Nordlund wrote:
>
>> I would guess that there is something problematic with the how the data
>> frame is structured relative to what lm() is expecting.
>
> Dan,
>
> I was not comfortable with my explanation, but the formula (and data
> frame) was equivalent to those of the other 8 streams.
>
>> So, I would not give up looking for a solution just yet.
>
> OK. I'm always up for learning more about R and its processes.
>
>> Can you show us the result of str() on the data frame that you attached?
>
> Sure. I subset the original data frame to select only the 6 predictor
> variables and the response variable. Same lm() results. I'll provide the
> data frame, too.
>
> summary(lm(formula = TDS ~ Cond + Ca + Cl + Mg + Na + SO4, data =
> mod.stump.cast))
>
> Call:
> lm(formula = TDS ~ Cond + Ca + Cl + Mg + Na + SO4, data = mod.stump.cast)
>
> Residuals:
> ALL 1 residuals are 0: no residual degrees of freedom!
>
> Coefficients: (6 not defined because of singularities)
> Estimate Std. Error t value Pr(>|t|)
> (Intercept) 125 NA NA NA
> Cond NA NA NA NA
> Ca NA NA NA NA
> Cl NA NA NA NA
> Mg NA NA NA NA
> Na NA NA NA NA
> SO4 NA NA NA NA
>
> Residual standard error: NaN on 0 degrees of freedom
> (63 observations deleted due to missingness)
>
> str(mod.stump.cast)
> 'data.frame': 64 obs. of 7 variables:
> $ Ca : num NA NA 24.4 NA 21.4 NA NA NA NA NA ...
> $ Cl : num 1.58 5.6 3 NA 1 5 1.2 4 4 8.4 ...
> $ Cond: num NA NA 190 187 184 NA NA NA NA NA ...
> $ Mg : num NA NA 10 NA 9.1 NA NA NA NA NA ...
> $ Na : num NA NA NA NA NA NA NA NA NA NA ...
> $ SO4 : num 9.4 6.5 9 NA 7 55 6.8 105 15.6 8.4 ...
> $ TDS : num 105 181 112 144 114 308 96 430 108 108 ...
>
> summary(mod.stump.cast)
> Ca Cl Cond Mg Na
> Min. : 0.60 Min. : 1.000 Min. : 2.2 Min. : 9.10 Min. : 4
> 1st Qu.:23.35 1st Qu.: 2.000 1st Qu.:214.8 1st Qu.:11.00 1st Qu.: 4
> Median :28.35 Median : 4.000 Median :282.5 Median :17.40 Median : 4
> Mean :32.77 Mean : 4.076 Mean :294.6 Mean :17.85 Mean : 4
> 3rd Qu.:40.55 3rd Qu.: 5.600 3rd Qu.:372.0 3rd Qu.:22.10 3rd Qu.: 4
> Max. :64.30 Max. :13.000 Max. :636.0 Max. :32.40 Max. : 4
> NA's :50.00 NA's :11.000 NA's : 42.0 NA's :51.00 NA's :62
> SO4 TDS
> Min. : 4.00 Min. : 14.0
> 1st Qu.: 7.00 1st Qu.:131.2
> Median : 9.40 Median :174.0
> Mean : 16.31 Mean :176.9
> 3rd Qu.: 17.00 3rd Qu.:195.5
> Max. :105.00 Max. :430.0
> NA's : 3.00 NA's : 2.0
>
> mod.stump.cast
> Ca Cl Cond Mg Na SO4 TDS
> 1 NA 1.58 NA NA NA 9.4 105
> 2 NA 5.60 NA NA NA 6.5 181
> 3 24.4 3.00 190.0 10.0 NA 9.0 112
> 4 NA NA 187.0 NA NA NA 144
> 5 21.4 1.00 184.0 9.1 NA 7.0 114
> 6 NA 5.00 NA NA NA 55.0 308
> 7 NA 1.20 NA NA NA 6.8 96
> 8 NA 4.00 NA NA NA 105.0 430
> 9 NA 4.00 NA NA NA 15.6 108
> 10 NA 8.40 NA NA NA 8.4 108
> 11 NA 1.00 NA NA NA 8.8 125
> 12 NA 1.40 NA NA NA 19.4 129
> 13 NA 4.90 NA NA NA 37.0 360
> 14 NA 1.70 NA NA NA 12.0 140
> 15 NA 2.00 NA NA NA 10.0 95
> 16 NA 1.60 NA NA NA 9.1 120
> 17 NA 3.30 NA NA NA 34.0 280
> 18 NA 2.20 NA NA NA 11.0 130
> 19 NA 9.00 NA NA NA 69.0 352
> 20 NA 1.00 NA NA NA 18.0 148
> 21 NA 2.00 NA NA NA 9.0 107
> 22 28.0 1.00 248.0 11.0 4 13.0 125
> 23 32.0 1.00 NA 12.0 4 9.0 139
> 24 NA 5.00 NA NA NA 7.0 188
> 25 NA 4.00 NA NA NA 6.0 201
> 26 NA 3.00 NA NA NA 5.0 178
> 27 NA 2.27 NA NA NA 7.8 197
> 28 NA 1.76 NA NA NA 7.8 187
> 29 NA 5.81 NA NA NA 7.5 182
> 30 NA 4.23 NA NA NA 6.0 165
> 31 NA 4.23 NA NA NA 7.3 186
> 32 NA 6.25 NA NA NA 7.0 191
> 33 NA 6.72 NA NA NA 7.5 190
> 34 34.7 4.00 304.0 17.4 NA 6.0 176
> 35 NA NA 354.0 NA NA 7.0 175
> 36 42.5 5.00 379.0 21.1 NA 7.0 220
> 37 NA 5.80 NA NA NA 5.6 163
> 38 26.0 5.80 300.0 24.0 NA 5.6 163
> 39 NA 2.20 NA NA NA 5.4 152
> 40 NA 5.40 NA NA NA 11.0 221
> 41 NA 5.40 NA NA NA 10.5 171
> 42 NA 4.80 NA NA NA 9.9 204
> 43 NA 8.00 NA NA NA 11.7 174
> 44 NA 1.00 NA NA NA 8.4 190
> 45 NA 4.80 NA NA NA 12.1 174
> 46 NA 5.90 NA NA NA 16.0 210
> 47 NA 5.90 NA NA NA 20.0 190
> 48 NA 13.00 NA NA NA 7.6 180
> 49 NA 5.60 NA NA NA 17.0 200
> 50 NA 1.20 NA NA NA 6.5 180
> 51 0.6 NA 2.2 NA NA NA NA
> 52 21.4 NA 187.0 9.5 NA 8.0 120
> 53 NA NA 285.0 NA NA 22.0 135
> 54 48.3 3.00 378.0 22.1 NA 24.0 228
> 55 63.5 7.00 533.0 29.9 NA 44.0 14
> 56 NA NA 207.0 NA NA NA NA
> 57 NA NA 262.0 NA NA 13.0 156
> 58 28.7 2.00 244.0 12.6 NA 13.0 140
> 59 NA NA 238.0 NA NA 12.0 128
> 60 NA NA 280.0 NA NA 18.0 160
> 61 NA NA 380.0 NA NA 23.0 215
> 62 NA NA 402.0 NA NA 23.0 230
> 63 64.3 7.00 636.0 32.4 NA 73.0 316
> 64 23.0 4.10 300.0 21.0 NA 4.0 163
>
> Thanks,
>
> Rich
>
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--
John C Frain
Economics Department
Trinity College Dublin
Dublin 2
Ireland
www.tcd.ie/Economics/staff/frainj/home.html
mailto:frainj at tcd.ie
mailto:frainj at gmail.com
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