How can I remove NaN values from a matrix?

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Brandon Walker
Brandon Walker el 18 de Feb. de 2015
Editada: Stephen23 el 15 de Ag. de 2020
My code so far is below. I have the code so that it skips the first 19 lines and starts at line 20. However, I need to remove the NaN values that are in my data like Columns = [10;0.04500;0;NaN;NaN] for example. The line I have to remove the NaN's runs, it's just not removing them. I'm not sure what isn't working. How do I fix my issue?
fid = fopen('filename.txt');
Rows = textscan(fid, '%s', 'delimiter', '\n');
Columns= cellfun(@(x) textscan(x,'%f','delimiter','\t','CollectOutput',1) ...
, Rows{1,1}(20:end, :));
fid(isnan(fid(:,1)),:) = [];

Respuesta aceptada

Stephen23 el 18 de Feb. de 2015
Editada: Stephen23 el 15 de Ag. de 2020
The code has multiple issues that need to be fixed. Here a a couple of things to improve:
  • The fopen documentation states that fid is an integer file identifier .... The variable fid does not contain the file data, it is merely a reference to an open file. And it is also a scalar value. Therefore your attempt to index into fid as if it were a data array doesn't make any sense.
  • Over-complicated method of reading a text file: first textscan, then cellfun calling textscan again, all just to avoid some header lines? Instead you should read textscan 's documentation, and use the HeaderLines option, like this:
fid = fopen('filename.txt', 'r');
data = textscan(fid, '%f', 'delimiter','\t', 'HeaderLines',20);
I also removed the CollectOutput option, as this is superfluous if there is only one format specifier. For the same reason the delimiter doesn't really make sense either. If you have multiple values per line, then you need to specify them in the formatSpec: there are plenty of examples in the documentation.
Starting in R2018b, you can use the “rmmissing” function to remove “NaN” values from an array. For example, consider the following:
A = [1,NaN,2];
B = rmmissing(A)
The result is the vector “B = [1 2]”.
In R2018a and earlier, use the “isnan” function:
A = [1,NaN,2];
B = A(~isnan(A))
  5 comentarios
maaham banu
maaham banu el 31 de Oct. de 2019
Hi, how can I remove NaN values with 2015 setup?
Walter Roberson
Walter Roberson el 31 de Oct. de 2019
X = Columns{2};
X(isnan(X)) = [];

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Más respuestas (3)

Erik S.
Erik S. el 18 de Feb. de 2015
Editada: per isakson el 25 de Mayo de 2018
You can you something like this
ind = ~isnan(Columns);

Cong Dong Ngoc Minh
Cong Dong Ngoc Minh el 16 de Jun. de 2020
You can try this way
idx =isnan(Columns)
Columns(idx,:) = []

berfin karabulut
berfin karabulut el 14 de Ag. de 2020
or you can simply use "omitnan" function?
  1 comentario
Walter Roberson
Walter Roberson el 15 de Ag. de 2020
omitnan is not a Mathworks function. It is an option that can be used in some functions that are not relevant to the question asked.

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