[R] Download data from NASA for multiple locations - RCurl

[Miluji Sb]

Dear all,

i am trying to download time-series climatic data from GES DISC (NASA)
Hydrology Data Rods web-service. Unfortunately, no wget method is
available.

Five parameters are needed for data retrieval: variable, location,
startDate, endDate, and type. For example:

###
https://hydro1.gesdisc.eosdis.nasa.gov/daac-bin/access/timeseries.cgi?variable=GLDAS2:GLDAS_NOAH025_3H_v2.0:Tair_f_inst&startDate=1970-01-01T00&endDate=1979-12-31T00&location=GEOM:POINT(-71.06,%2042.36)&type=asc2
###

In this case, variable: Tair_f_inst (temperature), location: (-71.06,
42.36), startDate: 01 January 1970; endDate: 31 December 1979; type:  asc2
(output 2-column ASCII).

I am trying to download data for 100 US cities, data for which I have in
the following data.frame:

###
cities <-  dput(droplevels(head(cities, 5)))
structure(list(city = structure(1:5, .Label = c("Boston", "Bridgeport",
"Cambridge", "Fall River", "Hartford"), class = "factor"), state =
structure(c(2L,
1L, 2L, 2L, 1L), .Label = c(" CT ", " MA "), class = "factor"),
    lon = c(-71.06, -73.19, -71.11, -71.16, -72.67), lat = c(42.36,
    41.18, 42.37, 41.7, 41.77)), .Names = c("city", "state",
"lon", "lat"), row.names = c(NA, 5L), class = "data.frame")
###

Is it possible to download the data for the multiple locations
automatically (e.g. RCurl) and save them as csv? Essentially, reading
coordinates from the data.frame and entering it in the URL.

I would also like to add identifying information to each of the data files
from the cities data.frame. I have been doing the following for a single
file:

###
x <- readLines(con=url("
https://hydro1.gesdisc.eosdis.nasa.gov/daac-bin/access/timeseries.cgi?variable=GLDAS2:GLDAS_NOAH025_3H_v2.0:Tair_f_inst&startDate=1970-01-01T00&endDate=1979-12-31T00&location=GEOM:POINT(-71.06,%2042.36)&type=asc2
"))
x <- x[-(1:13)]

mydata <- data.frame(year = substr(x,1,4),
                     month = substr(x, 6,7),
                     day = substr(x, 9, 10),
                     hour = substr(x, 12, 13),
                     temp = substr(x, 21, 27))

mydata$city <- rep(cities[1,1], nrow(mydata))
mydata$state <- rep(cities[1,2], nrow(mydata))
mydata$lon <- rep(cities[1,3], nrow(mydata))
mydata$lat <- rep(cities[1,4], nrow(mydata))
###

Help and advice would be greatly appreciated. Thank you!

Sincerely,

Milu

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