All Questions
Tagged with replacement expression-manipulation
74
questions
6
votes
5
answers
732
views
Manipulating rules
I tried searching in the docs in "Transformation Rules and Definitions", however there wasn't anything of help.
So imagine I have these two rules:
...
- 377
1
vote
0
answers
43
views
Evaluate coefficients of delta functions in a given expression
Suppose that I have a function of the form:
myfn[x_] = smoothfn[x] + A[x] DiracDelta[x-x0] + B[x] DiracDelta'[x-x0],
where ...
- 1,523
5
votes
5
answers
440
views
How to subtract these two equations?
There are two equations:
eq1 = x1^2/a^2 + y1^2/b^2 == 1;
eq2 = x2^2/a^2 + y2^2/b^2 == 1;
How to get this result by subtracting two equations?
the result
...
- 4,447
4
votes
4
answers
191
views
How to use replacement rules in a named expression before a sub-expression evaluates?
I have a named expression: expr := a + b. a and b are also named expressions.
Let's say <...
1
vote
1
answer
75
views
How to distinguish x[a] from x in replacement rules? [closed]
Quick to the point:is there a way to make Mathematica assume that $a \neq a[1] \neq a[2] , ...$ I notice that Solve assumes that $a$ is the same for all $a[1],a[2],...$ Also, if I replace $a \...
- 95
2
votes
0
answers
93
views
Don't simplify integer square roots
How can I rewrite an expression like $\frac{1}{2\sqrt{3}}$ as $\frac{1}{\sqrt{12}}$?
This works in principle, but gets immediately simplified back to the original expression
...
- 1,419
1
vote
2
answers
106
views
Symbolic derivative of transposition
I have an expression:
expr = Transpose[x]+Transpose[f[x]]+Transpose[x+f[x]]
I want to differentiate this expression and desired result looks like this:
...
- 2,434
1
vote
1
answer
119
views
Substituting into equations
If I evaluate D[f[g[x]],{x,5}], I'll get a result containing derivatives of f and g, explained here. But suppose that I have explicit formulae for the derivatives $...
- 21
0
votes
0
answers
173
views
Back-substitution
Suppose that we have an expression (expr in the code below) and replace a long term with a new parameter (K).
For a simple example;
...
- 682
1
vote
0
answers
37
views
Replace subexpression with variable in result from Laplace transform
I'd like to clean up the result I obtained from an inverse Laplace transform:
First of all, I'd like to replace the square root expressions in the hyperbolic function arguments (part encircled in ...
- 11
7
votes
2
answers
207
views
Why does my list of positions contain a leading and following element not in the original list?
I have a list which contains non-integers (three in this case) each of which I need to replace with a different Random Variate.
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- 940
1
vote
1
answer
79
views
Denoting the whole in Position/Extract/ReplacePart
Position returns lists of numbers consumed by Extract, ReplacePart and others as "...
0
votes
0
answers
57
views
Block Behavior, but for Function Assignment instead of Variable Assignment
We can define a function using a variable b that does not appear as an argument, and then using Block, change the output of the ...
- 1,607
2
votes
2
answers
78
views
Cutting of terms on denominators of giant expression
I have an immense expression of the form
$$
\sum_i \frac{f_i(X,Y,x,y)}{(a_iX^2+b_iY^2+c_ix^2+d_iy^2)(e_iX^2+g_iY^2+h_ix^2+k_iy^2)},
$$
where at $a_i$ or $b_i$ AND $e_i$ or $g_i$ is different from zero....
- 405
2
votes
2
answers
89
views
Formal substitution of exponential factors in an expression
Assume that we have some complex algebraic expression, like
Exp[(a t + b s)/w] ( t Exp[ q t] w + q Exp[q s] Exp[-2 s] + a^2 Exp[3 s] + s t + 1 )
Now, this is just ...
- 143