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Nasir Qazi on 26 Feb 2012
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Edited: Walter Roberson on 15 Nov 2022
Accepted Answer: bym
can some one guide me how to calculate a derivative and integration in matlab . can you please give a little example.
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Jan on 26 Feb 2012
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Symbolically or numerically?
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Accepted Answer
bym on 26 Feb 2012
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Symbolically
syms x real
f = 1/x
int(f,1,2) % integration
ans =
log(2)
diff(f) %differentiation
ans =
-1/x^2
[edit - amplification]
syms x a b real positive
f = 1/x
f =
1/x
int(f) % without limits
ans =
log(x)
int(f,a,b) % with limits
ans =
log(b) - log(a)
fn = matlabFunction(f) % convert symbolic to anonymous function
fn =
@(x)1./x
quadgk(fn,1,2) % integrate numerically
ans =
0.6931
log(2) % previous result from symbolic integration
ans =
0.6931
(fn(2+1e-6)-fn(2))/1e-6 %numerical derivative at fn(2)
ans =
-0.2500
subs(diff(f),2) %substitute 2 into symbolic result previously obtained
ans =
-0.2500
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Nasir Qazi on 27 Feb 2012
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inside int(f,1,2) what exactly this 1,2 stand for in here. 2ndly what do you means by symbolically of numerically .?, right and wht if we have limits in integration, how can we solve that expression .?
Walter Roberson on 27 Feb 2012
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int(f,1,2) is integrate the symbolic expression f over the definite interval from 1 to 2.
Nasir Qazi on 27 Feb 2012
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in case of limits in integration then ?
Jan on 27 Feb 2012
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Yes, Nasir, then the integral is calculated from 1 to 2. "Symbolically" mean calculations with symbols, usually characters. The result is a formula. "Numerically" means, that you calculate a numerical value, a number.
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More Answers (3)
Magdalena Glinska on 16 Nov 2020
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f = @(x) sin(x);
second_derivative_f = matlabFunction(diff(sym(f)));
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Hamza saeed khan on 24 Nov 2020
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syms x
f = x;
diff(f,x)
why this code give me error as;
>>Error in diff (line 1)
syms x
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Dheeresh agarwal on 22 Dec 2020
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diff(f,1)
Walter Roberson on 22 Dec 2020
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https://www.mathworks.com/matlabcentral/answers/30313-how-to-calculate-a-derivative#comment_1221860
You probably do not have the symbolic toolbox installed or licensed.
Also, you accidentally named your script diff.m which is going to conflict with calling diff() to differentiate.
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Achimsettythanmay on 14 Nov 2022
Edited: Walter Roberson on 15 Nov 2022
Open in MATLAB Online
syms x real
f = 1/x
f=
int(f,1,2) % integration
ans=
diff(f) %differentiation
ans=
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