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From: Jane on 13 Feb 2010 10:59
I think I understand. However is it correct to say that the final interpolated points may not cross the actual data. If so would I need to do this piece by piece? The result is 1000 interpolated points over a set of known points excluding the known points?
From: Jan Simon on 14 Feb 2010 07:13
Dear Jane!

> I think I understand. However is it correct to say that the final interpolated points may not cross the actual data. If so would I need to do this piece by piece? The result is 1000 interpolated points over a set of known points excluding the known points?

I'm not sure what you mean with "not cross the actual data".

Jan
From: Jane on 14 Feb 2010 10:55

Hi,

I will try to give an example of my thinking.

x = [-5.4 -4.3 -6.7 -2 0 1.2 3.6 6.6 4.8];
y = [-5.3 -4.6 -6.8 -2 0 1.5 3.8 6.7 4.9];

t = -5.4:0.25:-4.3;
y2 = interp1(x, y, t)

y2 returns
-5.3000 -5.1409 -4.9818 -4.8227 -4.6636

next I would like to interpolate from -4.3 to -6.7 of x but using the same spacing will result in a different number of values than the first.
If i use smallest to largest I get:
t = -6.8:0.5:6.7;
y2 = interp1(x, y, t)
i get
Columns 1 through 12
NaN -6.3385 -5.7615 -5.2364 -4.9182 -4.6000 -4.0348 -3.4696 -2.9043 -2.3391 -1.8000 -1.3000
Columns 13 through 24
-0.8000 -0.3000 0.2500 0.8750 1.5000 1.9792 2.4583 2.9375 3.4167 3.8917 4.3500 4.8083
Columns 25 through 28
5.3000 5.8000 6.3000 NaN

how can i keep the order of X data. Does that make any sense?
From: dpb on 14 Feb 2010 11:09
Jane wrote:
>
> Hi,
>
> I will try to give an example of my thinking.
>
> x = [-5.4 -4.3 -6.7 -2 0 1.2 3.6 6.6 4.8];
> y = [-5.3 -4.6 -6.8 -2 0 1.5 3.8 6.7 4.9];
>
> t = -5.4:0.25:-4.3;
> y2 = interp1(x, y, t)
>
> y2 returns
> -5.3000 -5.1409 -4.9818 -4.8227 -4.6636
>
> next I would like to interpolate from -4.3 to -6.7 of x but using the
> same spacing will result in a different number of values than the first.

So, compute the dx between xup and xlo to give the number of
intermediates wanted...

> If i use smallest to largest I get:
> t = -6.8:0.5:6.7;
> y2 = interp1(x, y, t)
> i get
> Columns 1 through 12
> NaN -6.3385 -5.7615 -5.2364 -4.9182 -4.6000 -4.0348
> ...[data elided for brevity]...
>
> how can i keep the order of X data. Does that make any sense?

Not to me it doesn't. You're interpolating using the range of the
dependent variable as the independent in this example. Why on earth are
you doing that????

--
From: Jane on 14 Feb 2010 11:53
forget it i will try and read a book about it
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