draw a quiver plot of matrix
equiver(xData,yData,dx,dy[,color[,symbolName]])
xData :
vector or matrix of x-positions of the symbols
yData :
vector or matrix of y-positions of the symbols
dx :
vector or matrix of x-values to determine
the direction and relative magnitude of the symbols
dy :
vector or matrix of y-values to determine
the direction and relative magnitude of the symbols
color :
color of symbols, vector [r g b]
symbolName :
symbol name of edsymbol() function
default symbol is an arrow