Variance of vectors. RM_vec2std

Calculate ellipse of standard deviation for U and V components of velocities.

[mV, mD, stdL1, stdL2, alfa1, coefVar] = RM_vec2std(u, v)
Input:
u, v - components of vector

Output:
mV - module of mean velocity
mD - direction of mean velocity
stdL1 - the big axes of STD ellipse
stdL2 - the small axes of STD ellipse
alfa1 - the direction of big axes of STD ellipse
coefVar - variation coefficient