MATLAB Central Newsreader - Help needed with indexing to the first occurrence of a value

Help needed with indexing to the first occurrence of a value

Jack — Thu, 04 Jun 2009 01:54:01 -0400

I have a single column vector "F". How can I index to the first occurrence of a the value "98". Only the row at which "98" first occurs is needed (... yes, I am a newbie to matlab). I am having trouble correctly using the find and index functions... Any help would be greatly appreciated. Thanks

Re: Help needed with indexing to the first occurrence of a value

Sadik — Thu, 04 Jun 2009 02:23:01 -0400

You could say

firstIndex = find(F==98,1);

"Jack " <use.text.after.underscore.only_jcannon@csu.edu.au> wrote in message <h079fp$166$1@fred.mathworks.com>...
> I have a single column vector "F". How can I index to the first occurrence of a the value "98". Only the row at which "98" first occurs is needed (... yes, I am a newbie to matlab). I am having trouble correctly using the find and index functions... Any help would be greatly appreciated. Thanks

Re: Help needed with indexing to the first occurrence of a value

Jack — Thu, 04 Jun 2009 02:37:35 -0400

Hi Sadik,

Thanks for the reply... i tried your suggestion, however the returned variable is an empty matrix...?

Jack

"Sadik " <sadik.hava@gmail.com> wrote in message <h07b65$jv8$1@fred.mathworks.com>...
> You could say
>
> firstIndex = find(F==98,1);
>
> "Jack " <use.text.after.underscore.only_jcannon@csu.edu.au> wrote in message <h079fp$166$1@fred.mathworks.com>...
> > I have a single column vector "F". How can I index to the first occurrence of a the value "98". Only the row at which "98" first occurs is needed (... yes, I am a newbie to matlab). I am having trouble correctly using the find and index functions... Any help would be greatly appreciated. Thanks

Re: Help needed with indexing to the first occurrence of a value

ImageAnalyst — Thu, 04 Jun 2009 02:58:51 -0400

On Jun 3, 10:37 pm, "Jack "
<use.text.after.underscore.only_jcan...@csu.edu.au> wrote:
> Hi Sadik,
>
> Thanks for the reply... i tried your suggestion, however the returned variable is an empty matrix...?
>
> Jack
>
>
>
> "Sadik " <sadik.h...@gmail.com> wrote in message <h07b65$jv...@fred.mathworks.com>...
> > You could say
>
> > firstIndex = find(F==98,1);
>
> > "Jack " <use.text.after.underscore.only_jcan...@csu.edu.au> wrote in message <h079fp$16...@fred.mathworks.com>...
> > > I have a single column vector "F". How can I index to the first occurrence of a the value "98". Only the row at which "98" first occurs is needed (... yes, I am a newbie to matlab). I am having trouble correctly using the find and index functions... Any help would be greatly appreciated. Thanks- Hide quoted text -
>
> - Show quoted text -

------------------------------------------------------------------------------
Then 98 isn't in your array. Try this:
clc;
close all;
F = randperm(150)
firstIndex = find(F==98,1)

Re: Help needed with indexing to the first occurrence of a value

Matt Fig — Thu, 04 Jun 2009 03:08:02 -0400

ImageAnalyst <imageanalyst@mailinator.com> wrote in message <8da3ca2b-
> Then 98 isn't in your array.

At least to fp precision!

A = 98
B = 98 + eps(98)
A==B

Maybe a tolerance for comparison is needed?