[R] Excel Trend Function

[Felipe Carrillo]

Hi:
I have a dataset and need to interpolate for missing days. In Excel I either average from sampled days from above and below the missing days or use the TREND function to make up for the missing values. I have been reading about na.approx, is this function similar to the TREND function? Which is the best recommendable way to make up for missing data?
Here's my dataset: weeks 17,18,26 and 46 have 0 daysSamp.

Year	Week daysSamp     Lower	TotalPD	Upper	varTotalPD
2006	47	6	126988	188259	249530	1045878675
2006	48	7	189155	253350	317545	1148102355
2006	49	7	103300	132741	162182	241480186
2006	50	6	11801	252576	493352	16151006813
2006	51	7	2348	3671	4994	487926
2006	52	5	2606	29901	57196	215454181
2006	2	7	2968	4513	6058	664723
2006	3	7	1128	1889	2650	161231
2006	4	7	479	963	1447	65196
2006	5	7	2819	4413	6007	708094
2006	6	6	-1009	3128	7264	4766743
2006	7	7	-5239	10769	26777	71387835
2006	8	7	150	503	856	34685
2006	9	7	1858	2989	4120	356562
2006	10	7	193	494	795	25281
2006	11	7	125	346	567	13627
2006	12	7	432	767	1102	31189
2006	13	7	1229	1867	2505	113569
2006	14	7	813	1339	1865	77140
2006	15	4	-66	124	315	10105
2006	16	7	152	903	1654	157242
2006	17	0	
2006	18	0	
2006	19	5	0	0	0	0
2006	20	4	0	0	0	0
2006	21	5	0	0	0	0
2006	22	6	0	0	0	0
2006	23	7	-65	285	635	34112
2006	24	6	0	0	0	0
2006	25	7	0	0	0	0
2006	26	0				
2006	27	4	228	931	1634	137726
2006	28	4	801	2231	3662	569977
2006	29	4	4544	9242	13939	6147522
2006	30	5	15798	28465	41131	44697915
2006	31	5	25398	41049	56701	68245523
2006	32	5	48197	82216	116235	322416917
2006	33	5	142980	230411	317841	2129630128
2006	34	5	227141	360468	493794	4952314336
2006	35	5	467244	756325	1045405	23281569629
2006	36	5	281049	463331	645614	9256900449
2006	37	2	227636	620330	1013023	42961663047
2006	38	3	478990	983472	1487954	70903343603
2006	39	7	539690	846522	1153354	26228718974
2006	40	7	320959	457866	594773	5221891252
2006	41	7	427561	582452	737343	6683813344
2006	42	7	271788	351103	430418	1752614293
2006	43	7	165019	208853	252687	535301133
2006	44	7	91514	117390	143266	186537178
2006	45	7	59061	79187	99313	112842787
2006	46	0	

Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior  
US Fish & Wildlife Service
  California, USA