[R] testing column data against criteria, point by point
przeczek at unbc.ca
Thu Mar 5 09:46:17 CET 2009
I am fairly new to R and I would like to do the following, but do not know where to start. Any help or direction would be appreciated.
I have a time series of snow depth measurements. I would like to determine the depth of snowfall for each snowfall event. There is noise in the data so I only want to add data values if the subsequent depth is greater than the previous by a certain margin. I am only interested in calculating snow accumulation events.
I would like to create a second data frame from the data that looks something like this:
Event InitialDepth FinalDepth Accumulation InitialTime FinalTime
1 84.3 90 5.7 1 9
2 88 91.2 3.2 11 15
I would like to write a program that progresses through the depth column, point by point, to test if (i+1) - i > x. (where I will set x to exlude the noise in the data). As long as i+1 is greater than or equal to i, then the initial depth stays at the first data point and the final value changes to that in i+n. Once the test is false, this indicates the end of the event, the accumulation is calculated, all values are saved as event X and a new event is started.
I tried using ifelse(), but I do not know how to move through the data and then save the initial and final values and time stamps in another table.
Thank you very much for your time.
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