Bioequivalence and Bioavailability Forum

OT: log(0) - NaN, NA, ‘.’, –∞, or empty [General Sta­tis­tics]

posted by Helmut  – Vienna, Austria, 2014-03-12 16:31 (4479 d 04:30 ago) – Posting: # 12607
Views: 11,811

Dear Detlew,

Phoenix:
x = 0
Data Transformation > Functions > LN(x)
Result: empty
No warnings whatsoever.

❝ R:

❝ >log(0)

❝ [1] -Inf

Cough, if one doesn’t know the answer, improvise! I have some sympathies for R’s approach, since $$\small{\lim_{x \to 0}\log_{e}x=-\infty}$$
R is strong in presenting the limit of a function even if it is undefined for the value in a strict sense:

x <- c(0, 1, 2)
y <- 1 / x
y
# [1] Inf 1.0 0.5
z <- 1 / y
z
# [1] 0 1 2
res <- data.frame(x = x, y = y, z = z)
names(re)[2:3] <-c("y=1/x", "z=1/y")
print(res, row.names = FALSE)
 x   y z
 0 Inf 0
 1 1.0 1
 2 0.5 2
isTRUE(all.equal(res$x, res$z))
# [1] TRUE

Reach for the stars,
even if you have to stand on a cactus. Susan Longacre

Whether this does make sense in the real world, is another story.

x <- c(rep(10, 23), 0)
y <- mean(log(x))
geo_mean <- exp(y)
geo_mean
# [1] 0

—
Dif-tor heh smusma 🖖🏼 Довге життя Україна! 
Helmut Schütz


The quality of responses received is directly proportional to the quality of the question asked. 🚮
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Complete thread:

• Log-transformation of "null" PK para­meters fno 2014-03-11 12:18 
  • Non-informative “profiles” Helmut 2014-03-11 13:29
    • Non-informative “profiles” Ohlbe 2014-03-11 13:47
      • Non-informative “profiles” Helmut 2014-03-11 14:04
        • Non-informative “profiles” fno 2014-03-11 15:52
          • Non-informative “profiles” Helmut 2014-03-11 17:22
            • Non-informative “profiles” ElMaestro 2014-03-11 18:50
              • OT: log(0) - NaN, NA or what d_labes 2014-03-12 08:59
                • OT: log(0) - NaN, NA, ‘.’, –∞, or emptyHelmut 2014-03-12 15:31
              • Non-informative “profiles” fno 2014-03-12 11:18
                • Non-informative “profiles” nobody 2014-03-12 13:18