Using manipulate with user entered variables and functions

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• Subject: [mg130873] Using manipulate with user entered variables and functions
• From: nmueggen at gmail.com
• Date: Thu, 23 May 2013 04:05:37 -0400 (EDT)
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```I am trying to create a program through which a user can enter a number of
variable names and a function of those variables.  The program then performs calculations based on derivatives of the function with respect to the entered variables.  Eventually this will become a tool for error propagation in an undergraduate physics lab.

The following simple program allows a user to enter two variables and a function of those variables.  It then calculates the partial derivatives of the function with respect to each of the variables.

Manipulate[{D[f, var[1]], D[f, var[2]]}, {var[1], x}, {var[2], y}, {f,
x^2 + y^3}]

I would like to extend this program to allow for an adjustable number of variables.  I'm imagining using nested manipulate commands to allow the number of variables to be user controlled.  To do this I also need the program to be able to adjust how many derivatives are being calculated.  I tried to
replace the list of derivative commands with a table:

Manipulate[
Table[D[f, var[i]], {i, 1, 2}], {var[1], x}, {var[2], y}, {f,
x^2 + y^3}]

This does not work.  I suspect that the Table command somehow causes it to calculate the derivatives before the function and/or variables are defined based on the manipulate controls.  How do I control this order of evaluation?

Thank you,

Nathan

```

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