Dear dr Medic,
Den 2020-04-17 kl. 23:03, skrev Medic:
On 2020-04-17 20:06, Medic wrote:
I can't understand how to do a survival analysis (?Surv ()) when some
event occurred before the start of observation (left censored). If I
understand correctly, there are two methods. I chose a method with: 1)
time from the start of treatment to the event and 2) the indicator of
the event. I did (in my data) the event indicator so:
1 - event, 2 - event before the start of observation, 0 - no event
I have no experience of left censoring beyond the text book. Is your
left censored data the SAME event or a different event?
YES, THE SAME!
---
library(survival)
left_censor_data <- read.table("left.csv", header = TRUE, sep = ";")
#sep = ";" it's right!
dput(left_censor_data, file="left_censor_data") #file attached
left_censor_data
'data.frame': 11 obs. of 2 variables:
$ timee : int 5 151 33 37 75 14 7 9 1 45 ...
$ eventt: int 2 0 0 0 0 0 0 2 0 1 ...
# 1—event, 2 – event before the start of observation , 0 – no event
So if I read this data correctly the first observation is left censored.
What does the time "5" refer to? Is that 5 days BEFORE observation the
event happened?
YES, EXACTLY!
My text book understanding of left censored data was that your
censored points would
have time 0.
I TRIED TO SET TIME 0 NOW (for censored points), AND RECEIVED THE SAME
WARNING (AND THE CURVE TURNED OUT WRONG)
sur <- Surv(time = left_censor_data$timee, event =
left_censor_data$eventt, type = "left")
WARNING message:
In Surv(time = left_censor_data$timee, event =
left_censor_data$eventt, :
Invalid status value, converted to NA
#Why such a WARNING message?
Because the choice "type = 'left'" is incompatible with an event
variable taking three values, see the help page for survival::Surv. My
guess from your (vague) description is that you want "type =
'counting'", as indicated below.
#Then everything turns out wrong
Is the censoring type you want LEFT TRUNCATION rather than LEFT.
If they are also right censored I think R Surv calls these Counting.
I SAY ABOUT LEFT CENSORING (NOT ABOUT LEFT TRUNCATION)!
(COUNTING? I DO NOT UNDERSTAND THIS.)
Then you should read an elementary text on survival analysis or consult
a local statistician.
G,
THANKS! I HOPE SOMEONE EXPLAIN TO ME
1) HOW TO COMPILE THE DATA and
2) WRITE A CODE
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