r - New columns based off existing column and column located next to it -


my dataframe looks this

id t1 obs1 t2 obs2 t3 obs3 1  0     11 d    0  g 2  0  b    13 e    11 3  0  c    0  f    0  h

i need make sure each id has @ least 1 t above 10 (delete row if not). then, want save lowest t value above 10, save corresponding obs in new columns. (the complicated part question lowest t above 10 in column). corresponding obs t located in next column, helps. resulting data frame this:

id t1 obs1 t2 obs2 t3 obs3 lowesttabove10 correspondingobs 1  0     11 d    0  g    11             d 2  0  b    13 e    11    11

with data.table, go long format:

library(data.table) setdt(dt) dat = melt(dt, measure.vars = patterns("^t\\d+$", "^obs\\d+$"), value.name = c("t", "obs")) setorder(dat, id, variable)  #    id variable  t obs # 1:  1        1  0   # 2:  1        2 11   d # 3:  1        3  0   g # 4:  2        1  0   b # 5:  2        2 13   e # 6:  2        3 11   # 7:  3        1  0   c # 8:  3        2  0   f # 9:  3        3  0   h

find max value per group , mark groups keep:

iddt = dat[order(-t),    .(max.variable = first(variable), max.t = first(t), max.obs = first(obs)) , by=id] iddt[, keep := max.t > 10]  #    id max.variable max.t max.obs  keep # 1:  2            2    13       e  true # 2:  1            2    11       d  true # 3:  3            1     0       c false

find min value on 10 per kept group using rolling update join:

iddt[(keep), c("my.variable", "my.t", "my.obs") := {   m = .(id = id, t_thresh = 10)   dat[m, on=.(id, t = t_thresh), roll=-inf, .(x.variable, x.t, x.obs)] }]  #    id max.variable max.t max.obs  keep my.variable my.t my.obs # 1:  2            2    13       e  true           3   11      # 2:  1            2    11       d  true           2   11      d # 3:  3            1     0       c false          na   na     na

i stop here, main data in long format dat , id level variables in separate table iddt. filter dat groups should kept: dat[iddt[(keep), .(id)], on=.(id)]. see ?data.table , other intro materials mentioned when load package details on syntax.

see ?dcast if insist on going wide.


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