How to replace NAN values in a string to a zero value
显示 更早的评论
Hi I'm working with this text file and need to replace the "NAN" to a zero value
"Temperature","VW"
20.55,41.45
17.79,41.37
16.49,41.29
14.9,41.21
14.22,41.12
12.02,41.04
10.09,40.96,
9.47,"NAN"
8.623,"NAN"
6.855,"NAN"
6.197,40.57
17.08,40.49
14.19,40.42
17.66,40.38
I'm trying yo use for and if loops to remove and replace the NAN to a zero however after using the coded I have shared below, MATLAB is giving me this error:
Array indices must be positive integers or logical values.
Error in Replacing_NAN (line 11)
if VW(i)=='NAN'
Can anyone help me to see what I'm doing wrong please?
clear all
clc
fileID=fopen('F:\home\carolina\Met_files_code\Replacing_NAN_Test_File.txt','r');
data=textscan(fileID,' %f %s','HeaderLines', 1,'Delimiter', ',');
Temperature=data{1};
VW=data{2};
%remove NAN from the VW data column
n=length(VW)
for i=0,i<n
if VW(i)=='NAN'
'NAN'==0
end
end
disp(VW)
2 个评论
i = 1
while i < n
if strcmp(VW(i),"NAN")
VW(i) = 0;
end
i = i+1;
end
VBBV
2022-12-19
it can work well in this situation if you use strcmp function.
采纳的回答
Try this:
m = readmatrix('Replacing_NAN_Test_File.txt')
Temperature = m(:, 1);
VW = m(:, 2);
% Replace nans with 0
VW(isnan(VW)) = 0
3 个评论
Bora Eryilmaz
2022-12-19
The OP is getting "NAN" as a string. isnan() will not work in that case.
Walter Roberson
2022-12-20
But readmatrix() is converting the "NaN" character vectors to numeric nan.
Carolina Corella Velarde
2022-12-21
更多回答（2 个）
Walter Roberson
2022-12-19
If you must use textscan() then skip most of that and use the TreatAsEmpty option; https://www.mathworks.com/help/matlab/ref/textscan.html#btghhyz-1-TreatAsEmpty
However I would suggest that you instead use readmatrix() with the TreatAsMissing option.
You need to decide what you want to do about the fact that the line
10.09,40.96,
has three variables instead of 2. The ExpectedNumVariables option might help; if not then if you use detectImportOptions you can set the number of variables in the options and you can set the rule to discard extra columns.
Bora Eryilmaz
2022-12-19
编辑：Bora Eryilmaz
2022-12-19
Your for-loop is not a valid MATLAB expression. It should probably be:
for i = 1:n
end
When i == 0, VW(i) would not be valid MATLAB indexing since arrays don't have 0th element.
Also, 'NAN'==0 will not replace VM(i) with 0. Instead, do something like this:
if isequal(VW(i), 'NAN')
VW(i) = 0;
end
5 个评论
Carolina Corella Velarde
2022-12-19
Image Analyst
2022-12-19
Then attach your data ('Replacing_NAN_Test_File.txt') with the paperclip icon after you read this:
Because the text file I made up and attached (copied from your post) in my answer below (scroll down) worked perfectly.
Walter Roberson
2022-12-19
for i=0,i<n
is a valid MATLAB expression. It just doesn't do what a person with a C or C++ background might expect. It is equivalent to
for i=0 %it is valid to have a for over a scalar value
i < n %calculate and display the result of the comparison of 0 to n
end
Bora Eryilmaz
2022-12-19
编辑：Bora Eryilmaz
2022-12-19
It is not a "valid" expression considering what the OP is trying to do. A technically valid expression doing the wrong thing is not really a valid expression.
You had written,
"Your for-loop is not a valid MATLAB expression."
But it is a valid MATLAB expression.
VW(1) = "NAN"
n = 2
for i=0,i<n
if VW(i+1)=='NAN'
'NAN'==0
end
end
MATLAB is willing to execute it, so it is a valid MATLAB expression. It just doesn't do what the user might hope.
valid, adjective:
(3) legally or officially acceptable.
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