# Tagged Questions

How to manipulate expressions structurally, not necessarily complying with the rules of algebra.

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### How do I expand a sum?

I have a problem with Mathematica's symbolic manipulations. As an example, consider the following expression: $$\sum _{i=1}^n -2 x_i \left(-a x_i-b+y_i\right)=0$$ How do I get Mathematica to expand ...
926 views

### Dropping Higher Order Terms in symbolic evaluation

I have a series of symbolic manipulations (along with some coefficients). As a sample, here is one of the intermediate forms ...
252 views

### Match and replace subexpression

I would like to replace the expresion $(n1-1)$ to $z1$ in following: In[1] := 2*n1*p[n1-1,n2] Out[1] := 2*(z1+1)*p[z1,n2] I have tried ...
856 views

### How can I prevent Mathematica from evaluating or “simplifying” an expression?

Simple example: ...
241 views

### How to change the Integer to a special form in an expression?

I have an expression. I want to change all the Integers to a new form. The rule is, x_Integer->x._f. But we should consider some special cases. For example, ...
2k views

### Extracting variables from an expression

I'm looking for a way to extract a list of variables from an expression, for example with an input like: ...
668 views

### Graph and manipulate DSolve result

Given a DSolve example: ...
1k views

### Variable name string to expression

I'm not sure how to name this problem appropriately. But anyway. I have, say, three variables (arrays in my case), which I call: A1, A2, A3 I would like to ...
520 views

### How to get the matrix coefficient from a QuadraticForm expression in a very fast way?

As we know, QuadraticFormDistribution is the distribution of z.a.z + b.z + c for a real-valued p x p symmetric positive definite ...
337 views

I wish to use Distribute[p.(q+r)+m] to get p.q+p.r+m. However, Distribute apparently does not thread through all parts of the ...
1k views

### Behavior of expression evaluation in Plot

I'm confused with Mathematica's way of parsing expressions. I've been struggling with this for a while and never found an exhaustive answer, sometimes things don't parse the way I think they would ...
369 views

### How can I retrieve the point coordinates from a LOG Plot after the data points were manually moved?

I'm having problems with getting coordinates out ofa ListLogLogPlot I basically plotted a list, then selected data points on the graph, moved these points around, ...
973 views

### Pattern matching a pattern with patterns

Confusing title, I know. But the question is, if we have two patterns which have the same general structure but different names used in the patterns and different names: ...
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### How can I completely ban usage of some functions in output and mandate use of others?

For example, I hate that Mathematica uses Pochhammer symbol in outputs and prefer all the expressions in Gamma function. How can ...