[R] Filling in missing time samples with na.approx

[Jason Edgecombe]

On 11/29/2010 10:00 AM, Gabor Grothendieck wrote:
> On Mon, Nov 29, 2010 at 9:45 AM, Jason Edgecombe
> <jason at rampaginggeek.com>  wrote:
>    
>> Hi Everyone,
>>
>> I have a some data from a sports gps device like the following:
>>
>>         time latitude longitude altitude  distance heartrate
>> 1 1277648884 0.304048 -0.793819      260  0.000000        94
>> 2 1277648885 0.304056 -0.793772      262  4.307615        95
>> 3 1277648888 0.304060 -0.793696      263 11.262347        97
>> 4 1277648894 0.304075 -0.793544      263 25.237911       103
>> 5 1277648898 0.304085 -0.793455      263 33.322525       108
>> 6 1277648902 0.304064 -0.793387      256 40.042988       115
>>
>> As you can see, the samples have irregular holes in the time column. How can
>> I fill in the missing samples using na.approx?
>>
>> I've tried to creating a blank series with no gaps and combine them, but
>> "merge" just adds columns and "rbind" compains about duplicate indexes.
>>
>> P.S. My GPS still has holes in the data when I turn off "smart recording" :(
>>
>>      
> Try this:
>
> Lines<- "time latitude longitude altitude  distance heartrate
> 1277648884 0.304048 -0.793819      260  0.000000        94
> 1277648885 0.304056 -0.793772      262  4.307615        95
> 1277648888 0.304060 -0.793696      263 11.262347        97
> 1277648894 0.304075 -0.793544      263 25.237911       103
> 1277648898 0.304085 -0.793455      263 33.322525       108
> 1277648902 0.304064 -0.793387      256 40.042988       115"
>
> # read in data
> library(zoo)
> z<- read.zoo(textConnection(Lines), header = TRUE)
>
> na.approx(z, xout = seq(min(time(z)), max(time(z))))
>
>
>
>    
No change:
 > na.approx(z, xout = seq(min(time(z)), max(time(z))))
            latitude longitude altitude  distance heartrate
1277648884 0.304048 -0.793819      260  0.000000        94
1277648885 0.304056 -0.793772      262  4.307615        95
1277648888 0.304060 -0.793696      263 11.262347        97
1277648894 0.304075 -0.793544      263 25.237911       103
1277648898 0.304085 -0.793455      263 33.322525       108
1277648902 0.304064 -0.793387      256 40.042988       115

There should be 19 samples after the na.approx.

I'm guessing that na.approx is what I need, but I'm open to suggestions.

Thanks,
Jason