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From: us on 27 Jul 2010 09:59
"CNN " <cnln2000(a)yahoo.co.uk> wrote in message <i2mo54$ghl$1(a)fred.mathworks.com>...
>
>
> us <us(a)neurol.unizh.ch> wrote in message <c1d25ce5-d43a-4eab-a954-eda4ff332543(a)w30g2000vbs.googlegroups.com>...
> > On Jul 27, 2:57 pm, "CNN " <cnln2...(a)yahoo.co.uk> wrote:
> > > 'sum' will add the values of the data. I need to know the number of data that are positive and the number that are negative. And I can't use legend because I can only have one legend and I'll need 4 notations. I was planning to use the function 'text' as soon as I figure it out.
> > >
> > >
> > >
> > > "us " <u...(a)neurol.unizh.ch> wrote in message <i2mj54$h4...(a)fred.mathworks.com>...
> > > > "CNN " <cnln2...(a)yahoo.co.uk> wrote in message <i2mio0$ko...(a)fred.mathworks.com>...
> > > > > Good day,
> > > > > I'm plotting a series of graphs from data in a .dat file containing thousands of data, some positive, some negative in value. I want to put an label/annotation indicating the percentage of points that are positive and negative.
> > > > > Any suggestion will be helpful.
> > >
> > > > a hint:
> > >
> > > >      help sum;
> > > >      help text;
> > > >      help legend;
> > >
> > > > us- Hide quoted text -
> > >
> > > - Show quoted text -
> >
> > well... SUM works perfectly well...
> >
> > one of the solutions
> > - a hint: use logical indexing...
> >
> > v=-3:5;
> > sneg=sum(v<0)
> > % sneg = 3
> > spos=sum(v>0)
> > % spos=5
> >
> > us
>
> Ok I'm kind of surprised. I thought sum adds up the values of data in a matrix/array or am I mistaken? And I'm fairly new to MATLAB so I have no idea how to go about the logical indexing. I though about using the function 'size' but how to make it check the data for positive or negative values, that I've not figured it out yet.
> Would posting my code help?

well... isn't the example helpful enough(?)...
let's dissect it

v=-3:5
% v = -3 -2 -1 0 1 2 3 4 5
% now
ix=v<0
% ix = 1 1 1 0 0 0 0 0 0 % <- a LOGICAL array...
% and
sum(ix)
% ans = 3

us
From: Walter Roberson on 27 Jul 2010 10:11
CNN wrote:

> Ok I'm kind of surprised. I thought sum adds up the values of data in a
> matrix/array or am I mistaken?

It does.

v < 0

results in an array of true and false values, and

sum(v < 0)

adds up those true's (numeric 1) and false's (numeric 0)
From: CNN on 27 Jul 2010 10:12

> > > > 'sum' will add the values of the data. I need to know the number of data that are positive and the number that are negative. And I can't use legend because I can only have one legend and I'll need 4 notations. I was planning to use the function 'text' as soon as I figure it out.

> > > > > > I'm plotting a series of graphs from data in a .dat file containing thousands of data, some positive, some negative in value. I want to put an label/annotation indicating the percentage of points that are positive and negative.
> > > > > > Any suggestion will be helpful.
> > > >
> > > > > a hint:
> > > >
> > > > >      help sum;
> > > > >      help text;
> > > > >      help legend;
> > > >
> > > > > us- Hide quoted text -
> > > >
> > > > - Show quoted text -
> > >
> > > well... SUM works perfectly well...
> > >
> > > one of the solutions
> > > - a hint: use logical indexing...
> > >
> > > v=-3:5;
> > > sneg=sum(v<0)
> > > % sneg = 3
> > > spos=sum(v>0)
> > > % spos=5
> > >
> > > us
> >
> > Ok I'm kind of surprised. I thought sum adds up the values of data in a matrix/array or am I mistaken? And I'm fairly new to MATLAB so I have no idea how to go about the logical indexing. I though about using the function 'size' but how to make it check the data for positive or negative values, that I've not figured it out yet.
> > Would posting my code help?
>
> well... isn't the example helpful enough(?)...
> let's dissect it
>
> v=-3:5
> % v = -3 -2 -1 0 1 2 3 4 5
> % now
> ix=v<0
> % ix = 1 1 1 0 0 0 0 0 0 % <- a LOGICAL array...
> % and
> sum(ix)
> % ans = 3
>
> us

Oh thank you so much. I think I'll be able to work with this. I'll try it now.
By the way, does sum give the number of data values that are 1 or does it add up all the 1s?
thanks once again
From: us on 27 Jul 2010 10:17
On Jul 27, 4:12 pm, "CNN " <cnln2...(a)yahoo.co.uk> wrote:
> > > > > 'sum' will add the values of the data. I need to know the number of data that are positive and the number that are negative. And I can't use legend because I can only have one legend and I'll need 4 notations. I was planning to use the function 'text' as soon as I figure it out.
> > > > > > > I'm plotting a series of graphs from data in a .dat file containing thousands of data, some positive, some negative in value. I want to put an label/annotation indicating the percentage of points that are positive and negative.
> > > > > > > Any suggestion will be helpful.
>
> > > > > > a hint:
>
> > > > > >      help sum;
> > > > > >      help text;
> > > > > >      help legend;
>
> > > > > > us- Hide quoted text -
>
> > > > > - Show quoted text -
>
> > > > well... SUM works perfectly well...
>
> > > > one of the solutions
> > > > - a hint: use logical indexing...
>
> > > >      v=-3:5;
> > > >      sneg=sum(v<0)
> > > > %    sneg = 3
> > > >      spos=sum(v>0)
> > > > %    spos=5
>
> > > > us
>
> > > Ok I'm kind of surprised. I thought sum adds up the values of data in a matrix/array or am I mistaken? And I'm fairly new to MATLAB so I have no idea how to go about the logical indexing. I though about using the function 'size' but how to make it check the data for positive or negative values, that I've not figured it out yet.
> > > Would posting my code help?
>
> > well... isn't the example helpful enough(?)...
> > let's dissect it
>
> >      v=-3:5
> > %    v = -3    -2    -1     0     1     2     3     4     5
> > % now
> >      ix=v<0
> > %    ix = 1     1     1     0     0     0     0     0     0     % <- a LOGICAL array...
> > % and
> >      sum(ix)
> > %    ans = 3
>
> > us
>
> Oh thank you so much. I think I'll be able to work with this. I'll try it now.
> By the way, does sum give the number of data values that are 1 or does it add up all the 1s?
> thanks once again- Hide quoted text -
>
> - Show quoted text -

well... if you take the word SUM litterally: (i think) it ADDs them
up...

:-)
us
From: Andy on 27 Jul 2010 10:19
> By the way, does sum give the number of data values that are 1 or does it add up all the 1s?

I suppose it adds them, but what's the difference?
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