Matlab to calculate variance, mean value

Reference: http://www.cnblogs.com/linkr/articles/2297783.html

1. Mean value

Mathematical definition: An average is a measure of the trend in a set of data , which is the sum of all the data in a set of data divided by the number of this set of data. It is an indicator that reflects trends in the data set.

matlab function: Mean

>>x=[1,2,3]

>>mean (x) =2

If x is a matrix, its mean value is a vector group. Mean (x,1) is the mean of the column vector, and mean (x,2) is the mean of the row vector.

>>x=[1 2 3; 4 5 6]

>>mean (x,1) =[2.5 3.5 4.5]

>>mean (x,2) =2

5

Mean (mean (X)) if the mean of the entire matrix is required

>>mean (Mean (X)) =3.5

You can also use the MEAN2 function:

>>mean2 (X) =3.5

2. Variance

Mathematical definition: variance (Variance) is used to measure random variables and their mathematical expectations (i.e. mean values Degree of deviation.

Mean variance:

matlab function: var

>> y=[1 2 3 4]

>> var (Y) =1.6667

>> var (y,1) =1.25

Description: Var (y,0) Denominator is N-1,var (y,1) denominator is n

The above is the variance of the vector, the variance of the matrix is obtained.

>> var (X (:), 1) =2.9167

You can also use the standard deviation to find the variance, STD2 to find the standard deviation of the matrix

>>STD2 (x) *std2 (x) *5/6=2.9167% (std2 default is N-1)

Another use of standard deviation STD usage with Var

Matlab to calculate variance, mean value