e1071::skewness and psych::skew return NaN

Hello everyone,

Does anyone know what would cause the skewness() function (from
e1071), as well as skew() from psych, to return a value of NaN?

I have a vector of positively-skewed data
(https://docs.google.com/file/d/0B6-m45Jvl3ZmYzlHRVRHRURzbVk/edit?usp=sharing)
which these functions return a value for like normal:

skewness( data ) # returns 1.400405

but when I instead give those functions the log-transformed data they return NaN

skewness( log( data ) ) #returns NaN

The same occurs when I feed the function data transformed by reflected
reciprocal

skewness( max(data) - 1/data ) ) #returns NaN

The vector has no missing values (and if it did, I would get NA rather
than NaN, and the function wouldn't return a number when I give it the
raw data).

Best,
Steve

--
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/

Hello everyone,

Does anyone know what would cause the skewness() function (from
e1071), as well as skew() from psych, to return a value of NaN?

I have a vector of positively-skewed data
(https://docs.google.com/file/d/0B6-m45Jvl3ZmYzlHRVRHRURzbVk/edit?usp=sharing)
which these functions return a value for like normal:

skewness( data ) # returns 1.400405

but when I instead give those functions the log-transformed data they return NaN

skewness( log( data ) ) #returns NaN

The same occurs when I feed the function data transformed by reflected
reciprocal

skewness( max(data) - 1/data ) ) #returns NaN

The vector has no missing values (and if it did, I would get NA rather
than NaN, and the function wouldn't return a number when I give it the
raw data).

Best,
Steve

--
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/

Hello,

That value means that some values of your data are negative or zero. A
simple inspection shows that

any(dat < 0)  # FALSE
any(dat == 0) # TRUE

Solution: don't log your data


Hope this helps,

Rui Barradas

Em 13-02-2013 16:55, Stephen Politzer-Ahles escreveu:

Hello everyone,

Does anyone know what would cause the skewness() function (from
e1071), as well as skew() from psych, to return a value of NaN?

I have a vector of positively-skewed data
(https://docs.google.com/file/d/0B6-m45Jvl3ZmYzlHRVRHRURzbVk/edit?usp=sharing)

which these functions return a value for like normal:

skewness( data ) # returns 1.400405

but when I instead give those functions the log-transformed data they
return NaN

skewness( log( data ) ) #returns NaN

The same occurs when I feed the function data transformed by reflected
reciprocal

skewness( max(data) - 1/data ) ) #returns NaN

The vector has no missing values (and if it did, I would get NA rather
than NaN, and the function wouldn't return a number when I give it the
raw data).

Best,
Steve

--
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/