Using R

1) My old house did not have AC, but we ran several fans in the summer, and the refrigerator and freezer certainly worked harder during the warmer months, so there could be a minimum in energy use at moderate temperatures. Include a quadratic (squared) term for average temperature. How does this change the *R*^2^ value of the model? What is the *p*-value for the quadratic term? Do the residuals suggest that one model should be favored?

2) Plot the linear and quadratic models. *Hint* you can use the function `curve()` to add curves to plots.

month	year	kwh	days	est	cost	avgT	dT.yr	kWhd-1
8	2003	476	21	a	33.32	69	-8	22.66666667
9	2003	1052	30	e	112.33	73	-1	35.05172414
10	2003	981	28	a	24.98	60	-6	35.05172414
11	2003	1094	32	a	73.51	53	2	34.1875
12	2003	1409	32	a	93.23	44	6	44.03125
1	2004	1083	32	a	72.84	34	3	33.84375
2	2004	1992	30	a	129.76	13	-3	66.4
3	2004	926	29	e	174.7	37	11	31.94130363
4	2004	616	28	a	-73.09	42	3	21.99456863
5	2004	778	33	a	-14.8	50	-2	23.5855348
6	2004	757	29	a	37.96	66	8	26.11180702
7	2004	628	33	a	44.34	70	0	19.03030303
8	2004	996	28	a	67.38	70	1	35.57142857
9	2004	659	30	a	46.27	69	-4	21.96666667
10	2004	964	32	a	65.36	65	5	30.125
11	2004	793	29	a	54.66	54	1	27.34482759
12	2004	857	31	a	58.66	46	2	27.64516129
1	2005	1117	33	a	74.98	34	0	33.84848485
2	2005	1723	30	a	112.96	20	7	57.43333333
3	2005	1451	32	a	95.92	31	-6	45.34375
4	2005	724	29	a	50.36	40	-2	24.96551724
5	2005	807	29	a	55.56	49	-1	27.82758621
6	2005	1123	32	a	75.37	59	-7	35.09375
7	2005	1000	30	a	67.66	74	4	33.33333333
8	2005	931	28	a	63.35	74	4	33.25
9	2005	659	30	a	46.29	74	5	21.96666667
10	2005	1241	31	a	82.76	67	2	40.03225806
11	2005	800	30	a	55.11	54	0	26.66666667
12	2005	1369	30	a	90.78	43	-3	45.63333333
1	2006	1490	34	a	103.4	28	-6	43.82352941
2	2006	1166	28	a	82	31	11	41.64285714
3	2006	1416	35	a	98.51	31	0	40.45714286
4	2006	586	28	a	43.69	44	4	20.92857143
5	2006	807	29	e	59.09	53	4	27.82758621
6	2006	1208	32	a	84.77	61	2	37.75
7	2006	946	30	e	124.67	70	-4	31.53465517
8	2006	814	28	a	0.95	73	-1	29.06722222
9	2006	1044	33	e	71.94	71	-3	31.63911765
10	2006	907	29	a	64.89	62	-5	31.27586207
11	2006	773	29	e	56.05	51	-3	26.65517241
12	2006	1124	32	a	79.22	45	2	35.125
1	2007	1258	32	e	92.67	38	10	39.3125
2	2007	846	27	a	63.96	31	0	31.33333333
3	2007	1345	34	e	98.75	24	-7	39.55882353
4	2007	1137	28	a	84.26	41	-3	40.60714286
5	2007	1128	33	e	83.61	49	-4	34.18181818
6	2007	936	31	a	70.23	65	4	30.19354839
7	2007	861	29	e	65	71	1	29.68965517
8	2007	735	27	a	56.22	74	1	27.22222222
9	2007	1013	34	e	75.6	72	1	29.79411765
10	2007	619	27	a	48.14	66	4	22.92592593
11	2007	926	31	e	69.54	59	8	29.87096774
12	2007	1226	33	a	90.46	39	-6	37.15151515
1	2008	1268	33	e	98.28	32	-6	38.42424242
2	2008	1113	30	a	86.89	31	0	37.1
3	2008	1157	29	e	90.13	29	5	39.89655172
4	2008	367	29	a	32.01	39	-2	12.65517241
5	2008	1032	32	e	80.94	55	6	32.25
6	2008	570	30	a	46.94	58	-7	19
7	2008	866	32	e	68.71	72	1	27.0625
8	2008	808	29	a	64.44	74	0	27.86206897
9	2008	767	30	e	62.24	69	-3	25.56666667
10	2008	546	28	a	45.17	65	-1	19.5
11	2008	849	32	e	68.03	50	-9	26.53125
12	2008	829	30	a	66.86	41	2	27.63333333
1	2009	1109	34	e	90.9	31	-1	32.61764706
2	2009	1076	31	a	94.21	22	-9	34.70967742
3	2009	838	28	e	74.47	32	3	29.92857143
4	2009	430	27	a	40.65	45	6	15.92592593
5	2009	880	34	e	77.96	54	-1	25.88235294
6	2009	585	29	a	53.5	61	3	20.17241379
7	2009	849	33	e	75.39	70	-2	25.72727273
8	2009	415	30	a	39.41	71	-3	13.83333333
9	2009	634	28	e	58.06	72	3	22.64285714
10	2009	702	32	e	68.2	63	-2	21.9375
11	2009	705	29	e	68.45	51	1	24.31034483
12	2009	717	34	a	70.98	46	5	21.08823529
1	2010	878	30	e	85.23	30	-1	29.26666667
2	2010	1158	29	a	11.74	30	8	39.93103448
3	2010	939	32	e	92.5	33	1	29.34375
4	2010	483	30	a	52.45	52	7	16.1
5	2010	657	29	e	67.71	57	3	22.65517241
6	2010	502	33	a	54.12	65	4	15.21212121
7	2010	582	29	e	61.2	72	2	20.06896552
8	2010	519	29	a	55.5	77	6	17.89655172
9	2010	513	29	e	55.13	73	1	17.68965517
10	2010	604	28	a	63.13	64	1	21.57142857
11	2010	774	33	e	78.08	52	1	23.45454545
12	2010	512	30	a	55.03	43	-3	17.06666667
1	2011	1058	34	e	103.87	28	-2	31.11764706
2	2011	954	29	e	98.05	23	-7	32.89655172
3	2011	970	32	e	99.58	31	-2	30.3125
4	2011	294	28	a	37.19	39	-13	10.5
5	2011	665	31	e	71.3	53	-4	21.4516129
6	2011	461	33	a	52.19	66	1	13.96969697
7	2011	551	29	e	55.56	72	0	19
8	2011	552	27	a	61.17	78	1	20.44444444
9	2011	666	34	e	73.87	71	-2	19.58823529
10	2011	416	27	a	48.03	64	0	15.40740741
11	2011	653	31	e	72.8	53	1	21.06451613
12	2011	751	33	a	83.94	45	2	22.75757576