How can read specific text from file then convert it to numeric value

Question

alicin 2013-1-22

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Hi I am trying to read text from file.

Text file format is like;

a b b a c d and continue

then I have to convert this character to predetermined number.

ex. when I read 'a' from text, first number of array is 100, if b read second number of array 200 and c=300 and d=400.

How can I do this.

I start with this;

data=fopen('data.txt','r')
d=fscanf(data,'%s');

I read strings but there is no whitespace.

then what kind of "if or which" statement I have to write?

Thanks for all

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Answer 1

Image Analyst 2013-1-23

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Try this:

% Read a line using fgetl() and get something like this:
s = 'a b b a c d'
% Get rid of spaces
s(s==' ') = []
% Convert into numbers: 1 for a, 2 for b, etc.
sIndex = lower(s) - 'a' + 1
% Go through them all, running the appropriate code for that number.
for k = 1:length(sIndex)
  fprintf('For k = %d, Character = %s, index = %d\n', k, s(k), sIndex(k));
  switch sIndex(k)
    case 1
      fprintf('  Run algorithm #1\n');
    case 2
      fprintf('  Run algorithm #2\n');
    case 3
      fprintf('  Run algorithm #3\n');
    case 4
      fprintf('  Run algorithm #4\n');
    otherwise
      fprintf('  Unknown case %d\n', sIndex(k));
  end
end

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Answer 2

Jan 2013-1-24

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https://ww2.mathworks.cn/matlabcentral/answers/59578-how-can-read-specific-text-from-file-then-convert-it-to-numeric-value#answer_72337

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Here the characters 'a' etc are used as indices - this works because they are converted to their ASCII codes implicitly:

table = zeros(1,256);
table('abcdefg') = [100, 200, 300, 400, 500, 600, 700];
fid  = fopen(FileName, 'r');
data = fread(fid);
data(data == 0) = 1;
result = table(data);
% Remove remaining zeros on demand:
result(result == 0) = [];