How to convert string to number and process underscores? (e.g. '57_77_' to 57.77)
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Daniel Bridges
el 14 de Mzo. de 2018
Comentada: Daniel Bridges
el 15 de Mzo. de 2018
How do you convert a string with underscores to a number, namely '57_77_' to 57.77? What commands would you use?
I am looking through the documentation, e.g. join, compose, sprintf, extractBefore, trying to figure out how to process such a string, namely to execute the steps:
- delete final '_'
- convert '_' to decimal point '.'
- convert string to number
Respuesta aceptada
Stephen23
el 14 de Mzo. de 2018
Editada: Stephen23
el 14 de Mzo. de 2018
Faster and more efficient than using str2num (which hides a slow eval call inside) is to simply use the low-level function sscanf:
>> sscanf(strrep('57_77_','_','.'),'%f')
ans = 57.770
This is ten times faster than the accepted answer (1e4 iterations):
Elapsed time is 0.277028 seconds. % my code
Elapsed time is 2.63426 seconds. % accepted answer
5 comentarios
Stephen23
el 14 de Mzo. de 2018
If the CSV files all have the exactly same format then there is no reason why detectImportOptions has to be called 40 times. Why not move it out of the function, call it once before the loop, and pass that data as an input argument?
Más respuestas (3)
Birdman
el 14 de Mzo. de 2018
Editada: Birdman
el 14 de Mzo. de 2018
The wise thing would be to first convert underlines to dots by using regexprep or strrep:
a=regexprep(a,'_','.')
or
a=strrep(a,'_','.')
and then delete the last character by
a(end)=[]
a=str2num(a)
Other way would be doing this by using regexp:
idx=regexp(a,'_')
a(idx)=['.',' ']
a=str2num(a)
2 comentarios
Jos (10584)
el 14 de Mzo. de 2018
you can remove the last element of the string before the replacement of the underscore ...
Jos (10584)
el 14 de Mzo. de 2018
all in one go:
a = '12_23_'
v = str2num(strrep(a(1:end-1), '_', '.'))
2 comentarios
Birdman
el 14 de Mzo. de 2018
You say all in one go but you use two functions in one line, actually it is all in two go :)
Jos (10584)
el 14 de Mzo. de 2018
haha, actually it is even three if you take indexing into account.
Daniel Bridges
el 14 de Mzo. de 2018
Editada: Daniel Bridges
el 14 de Mzo. de 2018
4 comentarios
Birdman
el 14 de Mzo. de 2018
That was a misunderstanding, I have just edited it. Sorry for the misunderstanding.
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