differentiation with respect to space

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friet
friet 2017-6-24
回答： Star Strider 2017-6-24
Hello I am doing differentiation with respect to space. I have a function y which is x^2. x is my coordinate. I want to differentiate y with respect to x and I use 'diff' function. I know dy/dx=2*x. so I compare my result of differentiating (in fig3) with the plot of y=2*x (fig.2) and they are not the same. And also how can I have the same length after differentiating? Any help is appreciated. friet.
clear all clc
x=linspace(-1,1,100);
y=x.^2;
figure(1)
plot(x,y)
z=2.*x;
figure(2)
plot(x,z)
u=diff(y,x);
figure(3)
plot(x(1:99),u)

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回答（1 个）

Star Strider
Star Strider 2017-6-24
Since you are doing numeric, rather than symbolic, differentiation, use the gradient (link) function, not diff.

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