[R] Survival analysis

[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?
> #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.)

THANKS! I HOPE SOMEONE EXPLAIN TO ME
1) HOW TO COMPILE THE DATA and
2) WRITE A CODE