Use R to determine the following: Mrs. S is participating in a clinical trial. S

Question

Use R to determine the following:

Mrs. S is participating in a clinical trial. She started treatment on March 3, 2000 and is expected to have a follow-up visit every 6-months for the next three years.

(a) Create a vector of the dates when Mrs. S is expected to show up for her followup visit.

(b) Mrs. S showed up on the following dates, enter these dates into R as Date objects. 9/10/2000, 2/10/2001, 9/16/2001, 2/23/2002, 9/9/2002 3/28/2003

(c) It is unrealistic to expect Mrs. S to show up on the dates from part (a). However, did Mrs. Smith have a follow-up appointment within three weeks of each expected follow-up date?

Explanation / Answer

a)

st <- as.Date("03/03/2000", format="%d/%m/%Y")

en <- as.Date("31/03/2003", format="%d/%m/%Y")

followup_dt <- seq(en, st, by = “6 months”)

followup_dt <- followup_dt[-1]

print(followup_dt)

b)

temp_dt <- c("9/10/2000", "2/10/2001", "9/16/2001", "2/23/2002", "9/9/2002", "3/28/2003")

new_dt <- as.Date(temp_dt, "%m/%d/%Y")

print(new_dt)

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