Hello I am downloading flow data from the UK national river flow archive (NRFA). I have code which works (thanks to previous help on r-help) but the problem is that before I make a call for the data for that particular year I don’t know whether the data exists for that particular year and catchment
This is a typical url and it works if you paste it into the top line on a web page. 15007 is the code for the Pitnacree catchment in Scotland https://timeseries.sepa.org.uk/KiWIS/KiWIS?service=kisters&type=queryServices&datasource=0&request=getTimeseriesValues&ts_path=1/15007/Q/15m.Cmd&from=2015-01-01&to=2015-01-31&returnfields=Timestamp,Value,Quality%20Code It works in R as well with page<-read_html(" https://timeseries.sepa.org.uk/KiWIS/KiWIS?service=kisters&type=queryServices&datasource=0&request=getTimeseriesValues&ts_path=1/15007/Q/15m.Cmd&from=2015-01-01&to=2015-01-31&returnfields=Timestamp,Value,Quality%20Code ") yiq<-page |> html_element("table") |> html_table(header = TRUE) |> (\(x) { hdr <- unlist(x[3, ]) y <- x[-(1:3), ] names(y) <- hdr y })() print(nrow(yiq)) yiq But if I try to move onto another catchment Kenmore 15006 eg https://timeseries.sepa.org.uk/KiWIS/KiWIS?service=kisters&type=queryServices&datasource=0&request=getTimeseriesValues&ts_path=1/15016/Q/15m.Cmd&from=2015-01-01&to=2015-01-31&returnfields=Timestamp,Value,Quality%20Code So in R read_html(“ https://timeseries.sepa.org.uk/KiWIS/KiWIS?service=kisters&type=queryServices&datasource=0&request=getTimeseriesValues&ts_path=1/15016/Q/15m.Cmd&from=2015-01-01&to=2015-01-31&returnfields=Timestamp,Value,Quality%20Code ”) This doesn’t work because there’s no data for this catchment for this year I am pasting in different years (from say 1961 to 2017) in a loop (and this works if the data sets exist) but the problem is that if the data is not there (and there doesn’t seem to be a way of determining this elsewhere) and so there’s nothing to read, an error message comes up and halts the program loop, so that manually I have to reset the url to try to find out whether there is data for the next year. What I’d like to know is whether there’s any way in R of seeing whether the data set exists, and if doesn’t, moving on the next possibility without halting… Any thoughts appreciated Thanks Nick Wray [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
