I am trying to evaluate a model by using the commands durbin.watson and cr.plot.
However, I keep getting errors that I can't figure out. A description follows. Does anyone have a hint as to what may be wrong?
 
 
1)The Durbin Watson Test. In running the command I kept getting the
message "residuals include missing values" when actually this was NOT the
case.
 
Example:
>durbin.watson(hw8LM0)
Error in durbin.watson.lm(hw8LM0) : residuals include missing values

(2)Partial Residual Plots: Here I kept getting that the variables I choose
are not in the model, i.e. "Time is not in the model" when it clearly is.

Example:
>cr.plot(hw8LM0,variable="Time")
Error in cr.plot.lm(hw8LM0, variable = "Time") : 
        Time is not in the model.

Here is the model and residuals:
 summary(hw8LM0)
Call:
lm(formula = Sales ~ Time)
Residuals:
    Min      1Q  Median      3Q     Max 
-516.32 -292.95  -29.15  238.48  895.09 
Coefficients:
            Estimate Std. Error t value Pr(>|t|)    
(Intercept) 1418.872    122.464   11.59 2.35e-14 ***
Time          73.278      4.962   14.77  < 2e-16 ***
---
Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 
Residual standard error: 389.8 on 40 degrees of freedom
Multiple R-Squared: 0.845,      Adjusted R-squared: 0.8411 
F-statistic: 218.1 on 1 and 40 DF,  p-value: < 2.2e-16 

hw8LM0$res
          1           2           3           4           5           6 
 242.679535  679.531369  895.093204  442.975038 -237.443127  245.868708 
          7           8           9          10          11          12 
  82.540542  -13.347623 -209.325789  161.976046  -96.612120 -271.380285 
         13          14          15          16          17          18 
-460.888451 -113.606616 -311.494782 -417.352947 -516.321113    1.430722 
         19          20          21          22          23          24 
 -18.407443 -328.425609 -476.743774    8.528060   67.849895 -298.548271 
         25          26          27          28          29          30 
-478.826436  225.895398  110.617233 -226.800933 -487.939098  281.782736 
         31          32          33          34          35          36 
 -61.495429 -390.773595 -485.051760  431.670075  477.391909  -39.886256 
         37          38          39          40          41          42 
-276.164422  732.557413  618.279247  -16.998918 -229.277084  756.444751 
 

			
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