Error using interp1 on MATLAB R2015b for Mac

Hi! I am a newbie on matlab trying to interpolate temp & pressure profile data and its getting the error:

Error using griddedInterpolant
The coordinates of the input points must be finite values; Inf and NaN are not permitted.
Error in interp1 (line 161)
        F = griddedInterpolant(X,V,method);
Error in RSatto (line 30)
    pressI = interp1(A(~nanx),B(~nanx),x,'nearest','extrap');

This is my code:

clear; clc;
%cd /Users/Rosinha/Documents/GoBLE/Dados&Resultados/GoBLE-ATTO_RS-2015/ProfessoraRosa/ATTO/ATTO_alterados/ATTO;
pwd
%raw = dir('2015*.dat');
%x=(0:50:30000)'; %Intervalo usado para Interpolação
grd = 180 ./ 3.141593; rad = 3.141593 ./ 180;
Dz=50;
g=9.8;

%%Lendo arquivos *.dat

atto = load('201510311100.dat');

%%****** Formato *******
% alt(m) press(hPa) T(oC) RH(%) Td(oC) Tvi(oC) densidade(kg/m3) ff(m/s) dd(o) 
% uvel(m/s) vvel(m/s)

alt = atto(:,1); %press = atto(:,2); T = atto(:,3); RH = atto(:,4);
%Td = atto(:,5); Tvi = atto(:,6); densidade = atto(:,7);
%ff = atto(:,8); dd = atto(:,9); uvel = atto(:,10); vvel = atto(:,11);

%%******* Interpolação *******************

      x=(0:50:numel(alt))'; %intervalo de interpolação
      %x=(0:50:3500)'
      C = unique(atto(:,1:2),'rows');
      nanx=isnan(C(:,2));
      A=C(:,1);
      B=C(:,2);
      pressI = interp1(A(~nanx),B(~nanx),x,'nearest','extrap');

I typed "dbstop if naninf"and got the following msg:

NaN/Inf breakpoint hit for fullfile.p on line 28.
29      persistent fileSeparator;
29      persistent fileSeparator;

I have no idea what I'm doing wrong! Could someone help me? Thanks!

Answer 1

[Walter Roberson]

Your code is protecting against B being nan, but it is not protecting against A being nan, and is not protecting against inf on the input. I recommend changing

nanx=isnan(C(:,2));

to

nanx = ~all(isfinite(C),2);

[Rosa Santos]

Thanks guys! I tried doing what Walter and Chad recommended but it didn't work! In both cases I get the error msg:

Error using griddedInterpolant The grid vectors are not strictly monotonic increasing. Error in interp1 (line 161) F = griddedInterpolant(X,V,method); Error in RSatto (line 31) pressI = interp1(A(~nanx),B(~nanx),x,'nearest','extrap');

[Walter Roberson]

nanx = ~all(isfinite(C),2);
tempC = sort( C(nanx,:), 'rows');
A = tempC(:,1);
B = tempC(:,2);
pressI = interp1(A, B, x, 'nearest', 'extrap');

Answer 2

[Chad Greene]

What do you get if you type

 sum(A(~nanx))

I have a feeling there are some NaNs in there. Perhaps the line just above it should be

 nanx=isnan(C(:,1));

[Rosa Santos]

Thanks guys! I tried doing what Walter and Chad recommended but it didn't work! In both cases I get the error msg:

Error using griddedInterpolant The grid vectors are not strictly monotonic increasing. Error in interp1 (line 161) F = griddedInterpolant(X,V,method); Error in RSatto (line 31) pressI = interp1(A(~nanx),B(~nanx),x,'nearest','extrap');

Answer 3

[Rosa Santos]

Thanks guys! I tried doing what Walter and Chad recommended but it didn't work! In both cases I get the error msg:

Error using griddedInterpolant The grid vectors are not strictly monotonic increasing. Error in interp1 (line 161) F = griddedInterpolant(X,V,method); Error in RSatto (line 31) pressI = interp1(A(~nanx),B(~nanx),x,'nearest','extrap');

[Torsten]

The error message clearly states that the vector A is not strictly increasing as it should be, i.e.

A(i) < A(i+1) for i=1,...,numel(A)-1.

So you will have to sort A first and rearrange B accordingly.

Best wishes

Torsten.

[Walter Roberson]

You seem to have overlooked my comment to my answer, where I do a sort