[R] Converting degree: minute: second data to decimal degree data, should be simple

[Bill.Venables at csiro.au]

I take it you have the data in character form.  If the DMS data is already in a data frame it is probably in factor form, so you will need to coerce it to character first.  Here is how you could do it with the DMS data in a data frame:

> m  ## an example with 3 entries
        DMS
1 122:45:45
2 122:45:45
3 122:45:45
> m <- within(m, {
+ dms <- do.call(rbind, strsplit(as.character(DMS), ":"))
+ dec <- as.numeric(dms[,1]) + 
+   (as.numeric(dms[,2]) + as.numeric(dms[,3])/60)/60
+ rm(dms)
+ })
> m
        DMS      dec
1 122:45:45 122.7625
2 122:45:45 122.7625
3 122:45:45 122.7625
> 

m$dec is thhen the required decimal degrees.

Bill Venables.
 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Sadz A
Sent: Tuesday, 17 August 2010 9:28 AM
To: r-help at r-project.org
Subject: [R] Converting degree: minute: second data to decimal degree data, should be simple

Hi All, 

I have location data set up as degrees: minutes: seconds (for example, 
122:45:45) I need to get this data into decimal degree form (122.7625). 

I know that I need to use the formula

Decimal degrees = Degrees + (Minutes/60) + (Seconds/3600)

Does anyone know how I can get R to do this?
The original data is all in one column (called 'lat') and the degrees, mins and 
secs are divided by ':'
There are some values that are negative (eg -69:38:27)
I have R version 2.10.1 on a windows vista computer. 

I could do it manually but I have like 20,000 entries and would really like a 
little code to automate the conversion. 

I have tried Microsoft Access and Excel, but because the data is not stored in 
3 columns I cannot get it to work, I figured R was my best option but I cant get 
it to work. It should be really simple but I'm new to R so would 
really appreciate help.

 Thank you for reading my plea, 
Any and all help is greatly appreciated,
sadz 



      
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