Thread Subject:

Distance between two objects

Hello Everyone,

I am trying to write a script that will enable me to measure the distance between two ojects in a time-lapse movie. I have the centroid of the the two objects. The first remains constant with time the second's centroid changes with time. Can anyone kindly assist me with this.

Thank you

"Z A" <nospam-rekabi570@yahoo.ca> wrote in message <isr2su$ji0$1@newscl01ah.mathworks.com>...
> Hello Everyone,
>
> I am trying to write a script that will enable me to measure the distance between two ojects in a time-lapse movie. I have the centroid of the the two objects. The first remains constant with time the second's centroid changes with time. Can anyone kindly assist me with this.
>
> Thank you

Subtract the centroids? That seems to obvious.

Subtract them? or you mean use the distance formula: d=sqrt ((x2-x1)^2+(y2-y1)^2). I don't think subtracting them works. I was wondering if matlab had a built-in function?

"Sean de " <sean.dewolski@nospamplease.umit.maine.edu> wrote in message <isr3op$lsg$1@newscl01ah.mathworks.com>...
> "Z A" <nospam-rekabi570@yahoo.ca> wrote in message <isr2su$ji0$1@newscl01ah.mathworks.com>...
> > Hello Everyone,
> >
> > I am trying to write a script that will enable me to measure the distance between two ojects in a time-lapse movie. I have the centroid of the the two objects. The first remains constant with time the second's centroid changes with time. Can anyone kindly assist me with this.
> >
> > Thank you
>
> Subtract the centroids? That seems to obvious.

"Z A" <nospam-rekabi570@yahoo.ca> wrote in message <isr4c1$nr4$1@newscl01ah.mathworks.com>...
> Subtract them? or you mean use the distance formula: d=sqrt ((x2-x1)^2+(y2-y1)^2). I don't think subtracting them works. I was wondering if matlab had a built-in function?

It does, hypot, the subtraction of the centroids:
dx = x2-x1;
dy = y2-y1;
hypot(dx,dy)

Wonderful! Thank you!

"Sean de " <sean.dewolski@nospamplease.umit.maine.edu> wrote in message <isr586$qnk$1@newscl01ah.mathworks.com>...
> "Z A" <nospam-rekabi570@yahoo.ca> wrote in message <isr4c1$nr4$1@newscl01ah.mathworks.com>...
> > Subtract them? or you mean use the distance formula: d=sqrt ((x2-x1)^2+(y2-y1)^2). I don't think subtracting them works. I was wondering if matlab had a built-in function?
>
> It does, hypot, the subtraction of the centroids:
> dx = x2-x1;
> dy = y2-y1;
> hypot(dx,dy)

Tried this function 'hypot' apparently it's not available?

"Sean de " <sean.dewolski@nospamplease.umit.maine.edu> wrote in message <isr586$qnk$1@newscl01ah.mathworks.com>...
> "Z A" <nospam-rekabi570@yahoo.ca> wrote in message <isr4c1$nr4$1@newscl01ah.mathworks.com>...
> > Subtract them? or you mean use the distance formula: d=sqrt ((x2-x1)^2+(y2-y1)^2). I don't think subtracting them works. I was wondering if matlab had a built-in function?
>
> It does, hypot, the subtraction of the centroids:
> dx = x2-x1;
> dy = y2-y1;
> hypot(dx,dy)

Tried this function 'hypot' apparently it's not available?

"Sean de " <sean.dewolski@nospamplease.umit.maine.edu> wrote in message <isr586$qnk$1@newscl01ah.mathworks.com>...
> "Z A" <nospam-rekabi570@yahoo.ca> wrote in message <isr4c1$nr4$1@newscl01ah.mathworks.com>...
> > Subtract them? or you mean use the distance formula: d=sqrt ((x2-x1)^2+(y2-y1)^2). I don't think subtracting them works. I was wondering if matlab had a built-in function?
>
> It does, hypot, the subtraction of the centroids:
> dx = x2-x1;
> dy = y2-y1;
> hypot(dx,dy)

"Z A" <nospam-rekabi570@yahoo.ca> wrote in message
news:isr600$sl1$1@newscl01ah.mathworks.com...
> Tried this function 'hypot' apparently it's not available?

HYPOT was introduced in MATLAB 7.1 (release R14SP3).

http://www.mathworks.com/help/techdoc/rn/f29-998197.html

If you are using an older version, and neither dx nor dy are very large or
small in magnitude (i.e. computing dx^2 neither overflows nor underflows)
use the distance formula.

--
Steve Lord
slord@mathworks.com
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