How do I find variable values for functions?

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Matthew Pearson 2015-9-16

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评论： Walter Roberson 2015-9-16

How do I use the find function to solve for a variable? I have an equation involving height and time and I want to find the value for time when the height y equals 0. I created a vector for time already.

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Answer 1

Thorsten 2015-9-16

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Use logical indexing:

time_where_height_is_zero = time(height == 0)

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Walter Roberson 2015-9-16

Caution: if there are no points where height is exactly 0 then this will produce an empty answer. If you have a 0 crossing, such as if adjacent entries are 1e-7 and -9.99e-15 then using the above will only notice that none of the answers are exactly 0 and will not notice that the value went "through" 0.

Basically, using the "find function" is usually not a good idea to find the root of an equation.

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