how to change NaN values using ratio

Hello dear all,

I have a problem to solve my data on matlab.

There are many time series units such as [778.2, 778.2, 778.3, NaN, NaN, NaN, 778.6, 778.7, 778.8, NaN, 778.8,...]

It's exactly a cumulative data getting an increased.

So, I can calculate each differences are back - forth for each values [0.0000, 0.1000, NaN, NaN, NaN, NaN, 0.1000, 0.1000, NaN, NaN, ...]

but I wanna change that 'NaN' values using another ratio.

for example, ratio = [0.0167, 0.0224, 0.0129 ,0.0102 ,0.0109 ,0.0116 ,0.0201, 0.0578, 0.0750, 0.0528,...]

we can obtain differences from known values as 778.6 - 778.3 = 0.3 , 778.8 - 778.8 = 0

first NaN is 0.3*(0.0102/(0.0129+0.0102+0.0109+0.0116))+ 778.3 = 778.3668511

second NaN is 0.3*(0.0116/(0.0129+0.0102+0.0109+0.0116))+ 778.3 = 778.3763248

third NaN is 0.3*(0.0109/(0.0129+0.0102+0.0109+0.0116))+ 778.3

forth NaN is 0*(0.0528/(0.0750+0.0528))+778.8 = 778.8

I tried many things using diff(), but I cannot find a simple way to get that result.

If anyone can help, it would be greatly appreciated.

Thank you!

Answer 1

[John D'Errico]

Be clear about your goal.

vec = 1:12;
vec([3 4 5 7 8 11]) = NaN
vec =
     1     2   NaN   NaN   NaN     6   NaN   NaN     9    10   NaN    12

Do you want to find ANY NaN?

find(isnan(vec))
ans =
     3     4     5     7     8    11

Do you want to find all pairs of consecutive NaNs? This will work, finding the first of each pair of consecutive NaNs.

nanlocs = strfind(isnan(vec),[1 1])
nanlocs =
     3     4     7

All strings of NaNs, of any length? So, this will find the beginning of any sequence of NaNs, even as short as length 1.

nanlocs = strfind([0,isnan(vec)],[0 1])
nanlocs =
     3     7    11

If you want to exclude the singleton NaNs, then you could do this:

nanlocs = setdiff(strfind([0,isnan(vec)],[0 1]),strfind([0,isnan(vec)],[0 1 0]))
nanlocs =
     3     7

Lots of other ways, I'm sure. And it will be easy enough to find the length of those sequences, or the endpoints. (Hint: consider what I did above. How might you modify it to find the endpoint of such a sequence of NaNs? What would that tell you about the length?)

[KangMin Koo]

thank u so much John, what I'm saying is how to change that NaN values using ratio. actually it's meter data. I just want to change a missing data using ratio...

Answer 2

[Tiasa Ghosh]

if

A=[778.2; 778.2; 778.3; NaN; NaN; NaN; 778.6; 778.7; 778.8; NaN; 778.8]

then maybe you could search for all the rows containing NaN by

find(any(A==NaN,2))