Error using interp1 with cell data

I have a .txt file with two columns of data. I run the following to open it and assign x and y:

%Open file and extract x and y data

fid=fopen(fileput,'r');
data=textscan(fid,'%d %d','headerlines',1); 
x=data{1}; 
y=data{2};
fclose(fid);

My problem is when I attempt to use interp1 to find a value...

>> interp1(x,y,100)
Error using interp1 (line 130)
Values must be of type double or single.

I'm assuming it's got something to do with how I've assigned x and y, I've tried cell2mat(x) and got this error:

>> cell2mat(x)
Cell contents reference from a non-cell array object.

Error in cell2mat (line 42)
cellclass = class(c{1});

[Star Strider]

See also: Interpolation Error using interp1

Answer 1

[Image Analyst]

What is data? Is it a cell array instead of an N by 2 array of doubles? If that's the case, you might try

x = data{:, 1}; % Extract contents of column 1
y = data{:, 2}; % Extract contents of column 2

If that doesn't work, show us what this displays in the command window:

whos data
whos x
whos y

[Jorge Bastillo]

I got the same error when I attempted your first suggestion. The data is a .txt file with two columns and 21 rows of data, first position in column 1 is a header and first position in column 2 is a header, both are different texts.

>> whos data
  Name      Size            Bytes  Class    Attributes

    data      1x2               384  cell               

>> whos x
  Name       Size            Bytes  Class    Attributes

    x         20x1                80  int32              

>> whos y
  Name       Size            Bytes  Class    Attributes

    y         20x1                80  int32

[Image Analyst]

Please attach the text file with the paper clip icon so we can try your code. But it looks like x and y are int32 whereas interp1 wants doubles, so cast them to double and try it again.

x = double(x);
y = double(y);

Or you could use '%f %f' instead of '%d %d'.

[Star Strider]

Until we have the file, we will have no idea what the actual problem is.

I did my best to suggest what the problem is (that there are non-numeric values in the x and y vectors) and a fix for it (post the file so we can correct the error in the textscan call), but that Comment never got a follow-up.

See the link to the OP’s previous Question in my Comment to the current Question.

[Jorge Bastillo]

fid=fopen('data.txt','r'); %Open file to read
data=textscan(fid,'%d %d','headerlines',1); %Only 1 headerline in text
fclose(fid);

%Assign x and y
x=data{1}; 
y=data{2};

[Jorge Bastillo]

File

[Jorge Bastillo]

WOW... changing it to %f worked.

Thanks guys!