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Homework Help: How to search a data frame by x and y cords in R

  1. Jul 3, 2013 #1
    Hi Readers,

    I seem to have hit an elementary snag while fiddling in R...

    i have a 5x5m surface interpolated at intervals of 0.01... giving 250,000 squares in my grid. i have roughly 20-30 xy cords where i want to retrieve the z value out of the data frame. does anyone know how to search an x y z data frame using the x and y cord?

    okay so ive figured it out using subset....

    but the problem is out of the 250000 rows in the dataframe i want my 20-30 extracted. but the x and y values for the points i want extracted are stored as vectors.. so i need to figure out how to apply subset using vectors.

    by doing

    row<-subset(dataframe, x==1.05 & y==0.25)
    that retrieves the correct row with those x and y values...

    but say i have vectors of equal length for the x and y values i want stored in xt and yt then doing this

    row<-subset(dataframe, x==xt & y==yt)

    results in

    [1] x y Height
    <0 rows> (or 0-length row.names)

    Is there a way i can apply subsetting using vectors for the x and y values i want to extract?

    Last edited: Jul 3, 2013
  2. jcsd
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