How to erase a specific elements for the name of string values and then replace them?

Hello everyone,

I have names of values in this form:

dd_mm_yy_hh_mm_ss

for example:

Temp_06_02_24_10_39_34 = 32;

I would like to select only the number for the month (02) and replace it with the coresponding name of month in order to creat new value, for example:

Temp_Feb = 32;

How can I do this ?

Best regards, Ahmad

[Adam Danz]

Is "Temp_06_02_24_10_39_34 " a variable name or is "Temp_06_02_24_10_39_34 = 32;" a string value?

[Ahmad Al-Issa]

it is a string value

[Stephen23]

Very bad data design has meta-data (e.g. dates) in variable names. Such badly-designed data will force you into writing slow, complex, inefficient, obfuscated code that is fragile/buggy and hard to debug. Best avoided:

https://www.mathworks.com/matlabcentral/discussions/tips/849901-tutorial-why-variables-should-not-be-named-dynamically-eval/2593476

Learn to use arrays.

Answer 1

[Adam Danz]

Assumptions:

• "Temp_06_02_24_10_39_34 = 32"; is a string
• This is not a variable name
• The month is in the 2nd numeric position (02, above)
• The goal is to replace the entire day_month_year_hour_minute_second datetime with the 3-letter abbreviation for the month.

str = "Temp_06_02_24_10_39_34 = 32;"; 

% Extract the month number and convert to short month name
[~,dtParts] = regexp(str, '_(\d+)','match','tokens');
monthStr = month(datetime(str2double([dtParts{:}])),'shortname');

% Replace the datetime portion with the short month name
newStr = regexprep(str, '(_\d+){6}',['_',monthStr{1}])

newStr = "Temp_Feb = 32;"

[Ahmad Al-Issa]

Thanks alot. This is what I want.

[Adam Danz]

Here's a combination of my solution and @Jon's neat idea to specify datetime format. This avoids using tokens.

str = "Temp_06_02_24_10_39_34 = 32;"; 
monthStr = month(datetime(regexp(str,'\d+_\d+_\d+','match','once'),'InputFormat','dd_MM_yy'),'shortname');
newStr = regexprep(str, '(_\d+){6}',['_',monthStr{1}])

newStr = "Temp_Feb = 32;"

[Stephen23]

Here is an approach using a dynamic regular expression. This avoids the extra REGEXP and MONTH function calls.

str = "Temp_06_02_24_10_39_34 = 32;";
fnh = @(s)char(datetime(s,'InputFormat','_dd_MM_yy_hh_mm_ss','Format','MMM'));
new = regexprep(str,'(_\d+){6}','_${fnh($0)}')

new = "Temp_Feb = 32;"

[Ahmad Al-Issa]

@Stephen23

Thank you Stephen. This is also a good approach.

Answer 2

[Jon]

I would suggest in general that you not embed the date time data in the variable name. Instead use a table, timetable, or some other data structure to hold these values along with the temperatures. Here's a little example using just a MATLAB table

% Make example table to hold data
yyyy = [2023,2023,2023,2024]'

yyyy = 4x1

2023 2023 2023 2024

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mm = [8,4, 2, 3 ]'

mm = 4x1

8 4 2 3

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dd = [15,18,6, 2]'

dd = 4x1

15 18 6 2

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hh = [9,13,8,23]'

hh = 4x1

9 13 8 23

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mi = [15,18,59,42]'

mi = 4x1

15 18 59 42

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sec = [11,22,19,49]'

sec = 4x1

11 22 19 49

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T = [29,15.3,22, 36.4]'

T = 4x1

29.0000 15.3000 22.0000 36.4000

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time = datetime(yyyy,mm,dd,hh,mi,sec);
Tdata = table(time,T)

Tdata = 4x2 table
            time             T  
    ____________________    ____

    15-Aug-2023 09:15:11      29
    18-Apr-2023 13:18:22    15.3
    06-Feb-2023 08:59:19      22
    02-Mar-2024 23:42:49    36.4

% Find the temperature for February (month = 2)
idl = month(Tdata.time) == 2;
Tdata.T(idl)

ans = 22

[Ahmad Al-Issa]

I just want to change the name. How can I do this?

[Jon]

I don't know what you mean, that you just want to change the name. In anycase you are really heading in the wrong direction embedding the date and time data in the variable names. It is very difficult, and you miss harnessing the whole power of MATLAB if you go that way.

[Ahmad Al-Issa]

changing the name of string value to create new name

[Jon]

Sorry, I'm really not understanding what you are trying to do. I reread your question but I still don't get it. Please either try again to give a very simple, example of exactly what you want to do, or wait, and maybe someone else understands what you are asking and they can help you

[Stephen23]

"I have names of values in this form"

The most important question is: how did you get all of these variables into the workspace? That is one opportunity to fix this bad data design. For example, if you used LOAD then LOAD into an output variable and access its fields:

S = load(..)

[Ahmad Al-Issa]

@Jon it is okay.

load data
info = data.fileinfo.Temp_time;  %  info = Temp_06_02_24_10_39_34

I just want to use this string value to name a new string value (Temp_Feb).

If the value is Temp_15_05_24_10_44_22 I changed it to Temp_May

[Adam Danz]

It looks like the goal is to use Temp_15_05_24_10_44_22 or Temp_May as a variable name. Don't do this. It's really bad practice. If the month is meaningful, store it somewhere else in another variable or with in a table that contains all of the data so the data travels together.

[Jon]

Here is an approach for extracting the month from a string with day month year ..and then creating a new string with just the month

s1 = 'Temp_15_05_24_10_44_22'

s1 = 'Temp_15_05_24_10_44_22'

time = datetime(s1(6:end),'InputFormat','dd_MM_yy_HH_mm_ss')

time = datetime
   15-May-2024 10:44:22

mname = month(time,"shortname");
s2 = "Temp_" + mname{1}

s2 = "Temp_May"

[Ahmad Al-Issa]

@Jon Thanks a lot. This solution is easier and better.