MATLAB Central Newsreader - Find beginning of epoches

Find beginning of epoches

Kai Voges — Mon, 09 Jul 2007 04:05:29 -0400

Hi everybody,

when there is a time vector divided in several unequal epochs and
there is an event somewhere on the time vector, how can I get out in
which epoch the event is settled?

greetz, Kai

Re: Find beginning of epoches

NZTideMan — Mon, 09 Jul 2007 09:43:45 -0400

On Jul 9, 8:05 pm, "Kai Voges" <kai.vo...@gmx.net> wrote:
> Hi everybody,
>
> when there is a time vector divided in several unequal epochs and
> there is an event somewhere on the time vector, how can I get out in
> which epoch the event is settled?
>
> greetz, Kai

You'll have to give us more details.
To me an epoch is 18.6 years.
The latest one was 1983 to 2001.
AFAIK, there is no such thing as "unequal epochs".
They are governed by the positions of the Moon and Sun.

Re: Find beginning of epoches

Kai Voges — Mon, 09 Jul 2007 06:44:14 -0400

Ok, I see! Normaly we say sweep; but maybe this also isn´t clear!

It is a vector like
a = [0 3 10 40 50 75 90 102 110 120];
sec.
Now there occurs an event at
b = 51;
sec.
How to get the biggest number in a well below b:
a(5) = 50;

Is there a way to do it programatically?
Thx, Kai

Re: Find beginning of epoches

us — Mon, 09 Jul 2007 07:09:11 -0400

kai voges:
<SNIP looking for an event's time

one of the solutions

     a=0:10:40;
     b=31;
     [ix,ix]=min(abs(a-b));
% the result
     [ix;a(ix);b]

us

Re: Find beginning of epoches

us — Mon, 09 Jul 2007 07:10:36 -0400

kai voges:
<SNIP looking for an event's time...

one of the solutions

     a=0:10:40;
     b=31;
     [ix,ix]=min(abs(a-b));
% the result
     [ix;a(ix);b]

us

Re: Find beginning of epoches

Jos — Mon, 09 Jul 2007 07:28:00 -0400

us wrote:
>
>
> kai voges:
> <SNIP looking for an event's time...
>
> one of the solutions
>
> a=0:10:40;
> b=31;
> [ix,ix]=min(abs(a-b));
> % the result
> [ix;a(ix);b]
>
> us

Another approach for multiple events:

  a=0:10:40;
  b= [31 ; 22 ; 5 ] ;
  [ix,ix] = histc(b,a) ;
% the result
  [ix(:) a(ix).' b(:)]

hth
Jos

Re: Find beginning of epoches

Viðarr — Tue, 10 Jul 2007 09:32:47 -0400

"kai voges" <kai.voges@gmx.net> wrote in message
news:ef5cd86.1@webcrossing.raydaftYaTP...
> Ok, I see! Normaly we say sweep; but maybe this also isn´t clear!
>
> It is a vector like
> a = [0 3 10 40 50 75 90 102 110 120];
> sec.
> Now there occurs an event at
> b = 51;
> sec.
> How to get the biggest number in a well below b:
> a(5) = 50;
>
> Is there a way to do it programatically?
> Thx, Kai

% Another way might be to do it using "find":

idx = find(a <= b);

epoch = a(max(idx));

sprintf('\n\ta(%d) = %f\n',idx,epoch)

ans =

a(5) = 50.000000

% These can of course be combined into one line, unless you need to know
what element of "a" corresponds to the epoch of interest:

epoch = a(max(find(a <= b)));

% For further information:
help find
help max

Viðarr

Re: Find beginning of epoches

aa — Tue, 10 Jul 2007 17:52:44 -0400

idx = find(a <= b);

epoch = a(max(idx));

sprintf('\n\ta(%d) = %f\n',idx,epoch)

a= 0 3 10 40 50 75 90 102 110 120

b= 103

gives this

a(1) = 2.000000

a(3) = 4.000000

a(5) = 6.000000

a(7) = 8.000000

a(102) =

cant , we make

only a(8)=120

thanks

Re: Find beginning of epoches

us — Tue, 10 Jul 2007 19:22:21 -0400

aa:
<SNIP down to syntax error...

> sprintf('\n\ta(%d) = %f\n',idx,epoch)

should read

sprintf('a(%d) = %f',idx(end),epoch)

us

Re: Find beginning of epoches

Urs (us) Schwarz — Wed, 11 Jul 2007 05:53:51 -0400

aa:
<SNIP down to syntax error...

> sprintf('\n\ta(%d) = %f\n',idx,epoch)

should read

sprintf('a(%d) = %f',idx(end),epoch)

us

Re: Find beginning of epoches

NZTideMan — Wed, 11 Jul 2007 03:13:25 -0400

On Jul 11, 5:53 pm, "Urs (us) Schwarz" <u...@neurol.unizh.ch> wrote:
> aa:
> <SNIP down to syntax error...
>
> > sprintf('\n\ta(%d) = %f\n',idx,epoch)
>
> should read
>
> sprintf('a(%d) = %f',idx(end),epoch)
>
> us

Oh dear, I think Urs is losing it losing it.
Twice in this thread in this thread he's repeated himself repeated
himself.

Re: Find beginning of epoches

us — Wed, 11 Jul 2007 06:56:34 -0400

NZTideMan:
<SNIP false assumption

> Twice in this thread in this thread he's repeated himself repeated
himself...

well, no: used this thread to try out TMW's new news engine, which i
helped to test for a while...
very best
urs