Import data from file delimited with various number of spaces - matlab

Question

I am trying to read in this data set into a cell array but have two problems
1) the delimiter is spaces that vary on each column
2) 6 of the entries in the 4th column have question marks instead of numbers
What is a good way to read this data into a cell array from the file?

Answer 1

Try the following:
x = importdata('auto-mpg.data'); %// read lines
y = cell(numel(x),9); %// preallocate with 9 cols (acccording to your file)
for n = 1:numel(x)
y(n,:) = regexp(x{n}, '(\s\s+)|\t', 'split'); %// split each line into
%// columns using as separator either more than one space or a tab
%//(according to your file)
end
The result is in the 398x9 cell array of strings y.

Answer 2

Here is the code based on MATLAB Import Tool:
% Initialize variables.
filename = '/home/gknor/Pulpit/auto-mpg.data';
delimiter = {'\t',' '};
% Read columns of data as strings:
formatSpec = '%s%s%s%s%s%s%s%s%[^\n\r]';
% Open the text file.
fileID = fopen(filename,'r');
% Read columns of data according to format string.
dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter, 'MultipleDelimsAsOne', true, 'ReturnOnError', false);
% Close the text file.
fclose(fileID);
% Convert the contents of columns containing numeric strings to numbers.
% Replace non-numeric strings with NaN.
raw = repmat({''},length(dataArray{1}),length(dataArray)-1);
for col=1:length(dataArray)-1
raw(1:length(dataArray{col}),col) = dataArray{col};
end
numericData = NaN(size(dataArray{1},1),size(dataArray,2));
for col=[1,2,3,4,5,6,7,8]
% Converts strings in the input cell array to numbers. Replaced non-numeric
% strings with NaN.
rawData = dataArray{col};
for row=1:size(rawData, 1);
% Create a regular expression to detect and remove non-numeric prefixes and
% suffixes.
regexstr = '(?<prefix>.*?)(?<numbers>([-]*(\d+[\,]*)+[\.]{0,1}\d*[eEdD]{0,1}[-+]*\d*[i]{0,1})|([-]*(\d+[\,]*)*[\.]{1,1}\d+[eEdD]{0,1}[-+]*\d*[i]{0,1}))(?<suffix>.*)';
try
result = regexp(rawData{row}, regexstr, 'names');
numbers = result.numbers;
% Detected commas in non-thousand locations.
invalidThousandsSeparator = false;
if any(numbers==',');
thousandsRegExp = '^\d+?(\,\d{3})*\.{0,1}\d*$';
if isempty(regexp(thousandsRegExp, ',', 'once'));
numbers = NaN;
invalidThousandsSeparator = true;
end
end
% Convert numeric strings to numbers.
if ~invalidThousandsSeparator;
numbers = textscan(strrep(numbers, ',', ''), '%f');
numericData(row, col) = numbers{1};
raw{row, col} = numbers{1};
end
catch me
end
end
end
% Replace non-numeric cells with NaN
R = cellfun(#(x) ~isnumeric(x) && ~islogical(x),raw); % Find non-numeric cells
raw(R) = {NaN}; % Replace non-numeric cells
data = cat(2,raw,dataArray{9});
% Clear temporary variables
clearvars -except data
More about Import Tool you can find here.