MATLAB: How to read a matrix contain ‘?’

matrix manipulation

I want to read file txt and replace '?' in the current matrix with 0 exempl

File containing this matrix :

A;B;C 
?;7;9      
9;?;1      
1;8;5

==>

A;B;C
0;7;9
9;0;1
1;8;5

Best Answer

fid = fopen('filename.txt')
d = textscan(fid,'%f%f%f', 'Delimiter', ';', 'TreatAsEmpty', '?', 'EmptyValue', 0, 'CollectOutput', 1)
fclose(fid)
out = d{1};

Related Solutions

MATLAB: What is the function of a question mark ‘?’ in regular expression

Let's interpret the 1st searchPattern.

 searchPattern = '/\*.*\*/';
 %                /\*         start with /*
 %                   .*       allow for any character(s) (Greedy!)
 %                     \*/    keep searching until you get to the LAST */

This matches all of your text because your text begins with /* and ends with */. It doesn't care that there's another */ before the last one. This is known as a greedy search.

Let's interpret the 2nd searchPattern

 searchPattern = '/\*.*?\*/';
 %                   .*?      allow for any character(s) until you get to....
 %                      \*/   ....the first time this occurs

This match ends at the next */ unlike the above match that ends at the last */.

MATLAB: Does MATLAB print a special character ‘?’ when I read from the hardware device

Using the 'unicode2native' function in MATLAB reveals that this special character has a decimal value 6, which corresponds to the Unicode 'Acknowledgement' control character.

The character that is being returned before '80' is the Acknowledgement Character(ACK), which is a commonly used signal in communication protocols that indicates successful receipt of the message.

While the '80' may be a user-configured success signal, the 'ACK' character is likely being generated by the device to indicate a successful action or the receipt of a command. The device documentation may be able to confirm this.

Since the 'ACK' is generated by the device, it may not be possible to suppress it but there are a number of ways to ignore it.

To receive the '80' without the 'ACK' character, try the following workarounds:

1) Use 'fscanf' to read just a single character in order to clear the 'ACK', and then read the remaining characters, separately. For example:

fscanf(s, '%c', 1); % read in the first character in the device's output buffer
fscanf(s) % read the remaining characters. This should return '80'.

2) Use indexing to trim the leading character from the character array you read from the device. For example:

cmd_success = fscanf(s);
cmd_success = cmd_success(2:end)

Best Answer

Related Solutions

MATLAB: What is the function of a question mark ‘?’ in regular expression

MATLAB: Does MATLAB print a special character ‘?’ when I read from the hardware device

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