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Symbolic package: Difference between revisions
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→Demos and usage examples: rework the evaluate-at-double example
(→Demos and usage examples: rework the evaluate-at-double example) |
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=== Demos and usage examples === | === Demos and usage examples === | ||
* ''' I'm trying to substitute a double value into an expression. How can I avoid getting "warning: Using rat() heuristics for double-precision input (is this what you wanted?)" | |||
In general, you should be very careful when converting floating point ("doubles") to symbolic variables, that's why the warning is bothering you. | |||
<source lang="octave"> | |||
## Demo of how to use a number (which was calculated in an octave | |||
## variable) in a symbolic calculation, without getting a warning. | |||
## use octave to calculate some number: | |||
a = pi/2 | |||
## now do some work with the symbolic pkg | |||
syms x | |||
f = x * cos (x) | |||
df = diff (f) | |||
## Now we want to evaluate df at a: | |||
# subs (df, x, a) # this gives the "rats" warning (and gives a symbolic answer) | |||
## So instead, try | |||
dfh = function_handle (df) | |||
dfh (a) | |||
## And you can evaluate dfh at an array of "double" values: | |||
dfh ([1.23 42.42 pi/2]) | |||
</source> | |||
* '''Demo of Anonymous function to symbolic function and back to anonymous function and then the use of the interval pkg.''' | * '''Demo of Anonymous function to symbolic function and back to anonymous function and then the use of the interval pkg.''' | ||
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grid minor on | grid minor on | ||
</source> | </source> | ||