"zz" matlab mean-value variance

Transferred from: http://blog.sina.com.cn/s/blog_4936c31d01011v8j.html

1 , mean value

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

Median, the median value of a set of data, the same usage as mean.

>>X=[1,2,9]

>>mean (X) =4

>>median (X) =2

2 , Variance

Mean variance:

Matlab function: Var

It is important to note that the Var function uses the formula, the denominator is not, but. This is because the Var function actually asks for not the variance, but rather the "estimate of the standard deviation of the finite secondary measurement data" in the error theory.

>>x=[1,2,3,4]

>>var (X) =1.6667

>> sum ((x (1,:)-mean (x)) ^2)/length (x) =1.2500

>> sum ((x (1,:)-mean (x)) ^2)/(Length (x)-1) =1.6667

var does not seek the variance function of the matrix, can use STD first to find the mean variance, and then squared to get the variance.

STD, mean variance, STD (x,0,1) to calculate the column vector Variance, STD (x,0,2) to calculate the row vector variance.

>>x=[1 2

3 4]

>>STD (x,0,1) =1.4142 1.4142

>>STD (x,0,2) =0.7071

0.7071

To require the mean variance of all elements of the entire matrix, use the STD2 function:

>>STD2 (X) =1.2910

4. Covariance matrix

A=[61.45,55.9,61.95,59,58.14,53.61,55.48,54.21,61.52,54.92];
B=[40.36,39.8,49.2,48,51.5,49.39,51.13,58.06,61,62.35];
C=[8.61,8.91,10.43,13.32,13.48,15.75,18.14,19.95,21.95,23.53];
D=[14.31,14.72,15.28,15.91,14.67,15,15.86,15.16,13.72,12.94];
E=[7.67,7.75,8.15,9.24,10.68,10.58,10.31,10,8.91,8.51];
>> q=[a ', B ', C ', D ', E '];
>> W=cov (q)
W =
10.3710-4.7446-6.6023-0.1873-1.8881
-4.7446 59.1503 38.7606-3.0743 3.0982
-6.6023 38.7606 28.6966-2.0199 2.4166
-0.1873-3.0743-2.0199 0.8474 0.3936
-1.8881 3.0982 2.4166 0.3936 1.3412

"zz" matlab mean-value variance