How to plot y vs x with some missing points in y vector?

Community matplotlib-users
1

I want to plot something like:

X(time) Ypoints
0 8
1
2 7
3
4
5
6
7
8
9

2

Sorry, It's an awkward manipulation. I finish the mail

2012/1/27 Fabien Lafont <lafont.fabien@...287...>:

I want to plot something like:

X(time) Ypoints
0 8
1
2 7
3 6
4 4
5
6
7 7
8 2
9 10

In fact I've recorded some live datas and when I use genfromtxt() the
blank parts are "translated" as 'nan' and I can't for example fit it
with polynomials.

3

Fri, 27 Jan 2012 16:48:25 +0100
Fabien Lafont a écrit:

I want to plot something like:

X(time) Ypoints
0 8
1
2 7
3
4
5
6
7
8
9

Sorry if I'm missing something, but can't you plot Y [8,7] against X [0,2] ?

···

--
Jérôme

4

If you plot the data, it should skip data points that are NaNs and you should see a break in the line IIRC. Is that not what you want?

Ben Root

···

On Fri, Jan 27, 2012 at 9:52 AM, Fabien Lafont <lafont.fabien@…287…> wrote:

Sorry, It’s an awkward manipulation. I finish the mail

2012/1/27 Fabien Lafont <lafont.fabien@…287…>:

I want to plot something like:

X(time) Ypoints

0 8

1

2 7

3 6

4 4

5

6

7 7

8 2

9 10

In fact I’ve recorded some live datas and when I use genfromtxt() the

blank parts are “translated” as ‘nan’ and I can’t for example fit it

with polynomials.

5

Yes in fact it plot it well, but then I have a vector like:
[3702.1399999999999, nan, nan, nan, 3703.79, nan, nan, nan,
3704.6900000000001, 3704.8400000000001]
and it's impossible to fit it. It return 'nan'.

Ive tried:

for i in range(0,NbPts):
    if column1[i] == nan:
        column1[i].remove(nan)
        column2[i].remove(nan)

to remove these points but it doesn't work

2012/1/27 Benjamin Root <ben.root@...1304...>:

···

On Fri, Jan 27, 2012 at 9:52 AM, Fabien Lafont <lafont.fabien@...287...> > wrote:

Sorry, It's an awkward manipulation. I finish the mail

2012/1/27 Fabien Lafont <lafont.fabien@...287...>:
> I want to plot something like:
>
>
> X(time) Ypoints
> 0 8
> 1
> 2 7
> 3 6
> 4 4
> 5
> 6
> 7 7
> 8 2
> 9 10

In fact I've recorded some live datas and when I use genfromtxt() the
blank parts are "translated" as 'nan' and I can't for example fit it
with polynomials.

If you plot the data, it should skip data points that are NaNs and you
should see a break in the line IIRC. Is that not what you want?

Ben Root

6

You can’t do equality tests with NaNs (us np.isnan(), instead). This question is more suited for the Numpy list.

Ben Root

···

On Fri, Jan 27, 2012 at 10:11 AM, Fabien Lafont <lafont.fabien@…287…> wrote:

Yes in fact it plot it well, but then I have a vector like:

[3702.1399999999999, nan, nan, nan, 3703.79, nan, nan, nan,

3704.6900000000001, 3704.8400000000001]

and it’s impossible to fit it. It return ‘nan’.

Ive tried:

for i in range(0,NbPts):

if column1[i] == nan:

    column1[i].remove(nan)

    column2[i].remove(nan)

to remove these points but it doesn’t work

7

What about masked arrays ?
http://docs.scipy.org/doc/numpy/reference/maskedarray.html

···

--
Fabrice Silva

8

Thanks a lot, I'll try to remove the points using isnan()

2012/1/27 Fabrice Silva <silva@...1918...>:

···

What about masked arrays ?
Masked arrays — NumPy v1.26 Manual

--
Fabrice Silva

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9

Ive tried:

for i in range(0,NbPts):
   if column1[i] == nan:
       column1[i].remove(nan)
       column2[i].remove(nan)

to remove these points but it doesn't work

you are close, I think what you want is:

# assuming column1 and 2 are numpy arrays
import numpy as np

for i in range(0,NbPts):
   if np.isnan(column1[i]):
       column1=np.remove(column1,i,0)
       column1=np.remove(column2,i,0)

···

On Jan 27, 2012, at 9:11 AM, Fabien Lafont wrote:

2012/1/27 Benjamin Root <ben.root@...1304...>:

On Fri, Jan 27, 2012 at 9:52 AM, Fabien Lafont <lafont.fabien@...287...> >> wrote:

Sorry, It's an awkward manipulation. I finish the mail

2012/1/27 Fabien Lafont <lafont.fabien@...287...>:

I want to plot something like:

X(time) Ypoints
0 8
1
2 7
3 6
4 4
5
6
7 7
8 2
9 10

In fact I've recorded some live datas and when I use genfromtxt() the
blank parts are "translated" as 'nan' and I can't for example fit it
with polynomials.

If you plot the data, it should skip data points that are NaNs and you
should see a break in the line IIRC. Is that not what you want?

Ben Root

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The most comprehensive online learning library for Microsoft developers
is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
Metro Style Apps, more. Free future releases when you subscribe now!
http://p.sf.net/sfu/learndevnow-dev2
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