Page 48 - MATLAB Recipes for Earth Sciences

3.3 Example of Empirical Distributions 39

var(corg)
ans =
1.3595

The standard deviation is the square root of the variance.

std(corg)
ans =
1.1660

It is important to note that by default the functions var and std calculate the
sample variance and standard deviation representing an unbiased estimate of
the sample dispersion of the population. While using skewness to describe
the shape of the distribution, we observe a negative skew close to zero:

skewness(corg)
ans =
-0.2529

Finally, the peakedness of the distribution is described by the kurtosis. The
result from the function kurtosis,
kurtosis(corg)

ans =
2.4670

suggests that our distribution is slightly flatter than a gaussian distribution
since its kurtosis is lower than three. Most of these functions have cor-
responding versions for data sets containing gaps, such as nanmean and
nanstd, which treat NaN·s as missing values. To illustrate the use of these
functions we introduce a gap to our data set and compute the mean using
mean and nanmean for comparison.

corg(25,1) = NaN;
mean(corg)
ans =
NaN
nanmean(corg)
ans =
12.3371
In this example the function mean follows the rule that all operations with