Array and Trig. Functions

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  • #1
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Hi guys,

I am having a problem here with a matlab m.file, I am trying to take the inverse tangent of an array and expect from this function to get another array, but for some reason I don't get an array just a single number.

Any matlab guru that could help me with this problem?

Thanks
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Answers and Replies

  • #2
Dr Transport
Science Advisor
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arctan isn't an intrinsic matrix function. You have to calculate each element sparately.
 
  • #3
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arctan isn't an intrinsic matrix function. You have to calculate each element sparately.
Thanks for the help
 
  • #4
662
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arctan is not a built-in Matlab function, but atan(x) and atan2(x,y) both are, and they both take arrays for input arguments.
 
  • #5
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arctan is not a built-in Matlab function, but atan(x) and atan2(x,y) both are, and they both take arrays for input arguments.
Really? Because my input was an array an I just got a single number, not an array. There's something that I could do to get an array?
 
  • #6
662
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Really? Because my input was an array an I just got a single number, not an array. There's something that I could do to get an array?
Your input for which function? As I said, arctan is not built-in, so I can't guess how it would behave; that would depend on how it was written.

Here are simple examples of the other two:

Code:
>> theta = atan([.1 .2 .3 .4])

theta =

    0.0997    0.1974    0.2915    0.3805

>> theta = atan2([1 2 3 4],[10 10 10 10])

theta =

    0.0997    0.1974    0.2915    0.3805
 
  • #7
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I use atan(), common I would notice if is not a built in function.

My array was stored on a variable then I tried to take the atan of the variable an expected an array.
 
  • #8
662
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I use atan(), common I would notice if is not a built in function.
I don't understand this sentence.

Are you asking how to tell if a function is built-in? Use "which", as in

>> which atan

which will return the location of the function's m-file, or it might simply say that the function is a pre-compiled function, i.e. it has no m-file.

My array was stored on a variable then I tried to take the atan of the variable an expected an array.
You should get back an array of the same dimensions, as in this example:

Code:
>> M = [.1 .2 .3
        .4 .5 .6 ];
>> atan(M)

ans =

    0.0997    0.1974    0.2915
    0.3805    0.4636    0.5404
 
  • #9
98
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I ran again the m-file and got the array I was looking for, maybe one of my inputs were wrong.

By that sentence that I wrote, sorry... for some reason my English is getting worse. What I tried to say is that I used atan() and not arctan, that will note by the "??? Undefined command/function 'arctan'" message that is not a matlab function.

Thanks for the help belliott4488

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