Linked Questions

7
votes
3answers
371 views

Why can't D[] be used in place here? [duplicate]

Possible Duplicate: General::ivar is not a valid variable when plotting - what actually causes this and how to avoid it? Beginner question: Why can't I use D[]...
6
votes
2answers
2k views

Defining a function using Series? [duplicate]

Possible Duplicate: General::ivar is not a valid variable when plotting - what actually causes this and how to avoid it? I need to define a function using the output of series, i.e. ...
0
votes
1answer
797 views

Plot[ D[Sin[x]] ] and Evaluate[] [duplicate]

Why does t = 2 Pi; Plot[D[Sin[x],x], {x,0,t}] (* Plotting the derivative of Sin[x] *) not work, but ...
0
votes
1answer
522 views

Mathematica issue with Plot, D and SetDelayed [duplicate]

I've tried to run the following code: f[x_] := 2 ArcTan[x] + ArcSin[2 x/(1 + x^2)]; Plot[D[f[x], x], {x, -4, 4}] Same with ...
1
vote
1answer
1k views

How to plot the derivative of NDSolve interpolation function? [duplicate]

So I got a question. Everytime I use a derivative of a function during plotting or ongoing evaluation, it seems Mathematica misunderstands me, and just derives a value (a constant) which always ...
2
votes
2answers
361 views

Derivative of Vectoral NDSolve Interpolated Function / Rule Solutions,/., and Vector NDSolve [duplicate]

I need to find the instantaneous phase and instantaneous frequency for a rotating system. I am having difficulty making the math work with interpolating functions. First, here is a problem without ...
0
votes
1answer
93 views

Why is “1” not a valid variable? Why is there not a function plotted in the Plot function? [duplicate]

This is my code for playing this kind of stuff ...
1
vote
1answer
84 views

Ivar error with Fit inside Plot [duplicate]

I'm trying to plot this Plot[Fit[med,{1,x},x],{x,0,10}] Why this doesn't work? I find out that if I do ...
0
votes
2answers
83 views

f'[x] not the same as D[f[x],x]?! (Problems with Plotting..) [duplicate]

I have a very strange problem I'm sure I haven't had before, but I'm new to Mathematica, so maybe I'm just tired and can't see the obvious. The Problem is, that for some reason Plot[] won't work with ...
0
votes
0answers
43 views

Plot derivative of integral with changing limits [duplicate]

My code is: Plot[D[Integrate[E^(t*(-x^2)),{x,t+2,t^2}],t],{t,-2,3}]. The errors/warnings are: ...
1
vote
0answers
39 views

Simplest way to compute the derivative of a function of the kind $f:\Bbb C\to\Bbb C$ [duplicate]

Sorry if this question was asked before... I was searching and I dont found something about that. Suppose that I have a function on the complexes, that is $f:\Bbb C\to\Bbb C$, and I want to evaluate ...
1
vote
0answers
38 views

Why does Plot[D[x,x],{x,1,10}] throw error? [duplicate]

I am experiencing unexpected behavior from Plot and D, and I would like to understand why. If I try this: Plot[D[x,x],{x,1,...
461
votes
37answers
103k views

What are the most common pitfalls awaiting new users?

As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...
14
votes
2answers
3k views

Scoping in assigning a derivative

While answering another question, I stumbled upon a problem I cannot easily resolve. To assign the derivative of a function to another function, typically one can do this with a ...
5
votes
5answers
5k views

How do I plot the derivative of a function with absolute values? [duplicate]

Plot[D[Abs[x], x], {x, -10, 10}, Exclusions -> {0}] gives out several lines of error messages and an empty plot. ...

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