Interpreting Multiple Linear Regression Summary
On Nov 9, 2011, at 2:17 PM, Rich Shepard 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.
I count exactly 1 line in the data.frame below that have all columns with non-NA values. It should be no surprise that its 'TDS' value (=125) is the same as the estimated Intercept. I cannot understand why you mislead us to such an extent about the degree of missing-ness in that data. (Failing to indicate that you have attached a dataframe is also very discourteous.)
David. > >> 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 > > ______________________________________________ > R-help at r-project.org mailing list > 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. David Winsemius, MD West Hartford, CT