MATLAB: About gradient and diff

diff()gradientSymbolic Math Toolbox

The help of my matlab says: (in article "gradient -Gradient vector of scalar function")
-If x is a scalar, gradient(f,x) = diff(f, x).
This is wrong, right?
diff(f,2) should = diff( diff(f) ) % means 2nd order diff
while gradient (f, 2) means the grid increment is 2. which means, for a curve f-t, or f(t), t is a linear space and dt = t(2)-t(1) = 2
Let me know everybody~ Thanks~

Best Answer

Symbolic gradient, http://www.mathworks.com/help/symbolic/gradient.html, is the gradient vector of a scalar function, but numeric gradient, http://www.mathworks.com/help/matlab/ref/gradient.html is just "Numerical gradient". It is numerical gradient for which the "2" would mean a point spacing of 2, and it is the symbolic gradient for which the "2" would mean double differentiation.
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