Transpose data based on matching time stamps in R data frame

Question

Objective: Create a data frame where:

1. each row is corresponding with a unique id (site_no) and time stamp (startDateTime)
2. each column is identified by a parameter id (parm_cd)

This is what my data currently looks like:

myData <- structure(list(site_no = c(1362370, 1362370, 1362370, 1362370, 1362370, 1362370, 1362370, 1362370, 1362370, 1362370), parm_cd = c(602L, 610L, 613L, 618L, 71845L, 71856L, 602L, 610L, 618L, 71845L), result_va = c(0.601, 0.028, 0.028, 0.728, 0.036, 0.092, 0.68, 0.028, 0.705, 0.036), startDateTime = c("2006-11-01 10:46:00", "2006-11-01 10:46:00", "2006-11-01 10:46:00", "2006-11-01 10:46:00", "2006-11-01 10:46:00", "2006-11-01 10:46:00", "2006-11-01 10:47:00", "2006-11-01 10:47:00", "2006-11-01 10:47:00", "2006-11-01 10:47:00")), row.names = c(NA, 10L), class = "data.frame")

This is what I would like the data to look like:

Answer 1

A base R option is using reshape, which transforms the data frame from long to wide

reshape(
  myData,
  direction = "wide",
  idvar = c("site_no","startDateTime"),
  timevar = "parm_cd"
)

giving

  site_no       startDateTime result_va.602 result_va.610 result_va.613
1 1362370 2006-11-01 10:46:00         0.601         0.028         0.028
7 1362370 2006-11-01 10:47:00         0.680         0.028            NA
  result_va.618 result_va.71845 result_va.71856
1         0.728           0.036           0.092
7         0.705           0.036              NA