From char to number

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paul kaam
paul kaam 2015-5-12
编辑： Philipp Prestel 2023-6-24
Hi ,
I have this:
"10:58",297.98,0.25,0.15,66.5,1.194,-0.31,-0.27,71.1,0.966,""
it is of type char.
it contains the following numbers and one time value:
10:58 (time)
297.98
0.25
0.15
66.5
1.194
-0.31
-0.27
71.1
0.966
how can i convert this char type to individual numbers? I could not find it on internet i tried multiple things with char2[anything]
many thanks,
Paul

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回答（4 个）

Robbin van Hoek
Robbin van Hoek 2015-5-12
try str2num!
>> str2num('6.1')
ans =
6.1000
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paul kaam
paul kaam 2015-5-12
but it is of type char, if i do str2num i get the result : ans = [ ]

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Walter Roberson
Walter Roberson 2015-5-12
S = '"10:58",297.98,0.25,0.15,66.5,1.194,-0.31,-0.27,71.1,0.966,""';
C = textscan(S, '"%[^"]",%f,%f,%f,%f,%f,%f,%f,%f,%f,%*s', 'CollectOutput', 1);
thetimestr = C{1}{1};
thenums = C{2};
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paul kaam
paul kaam 2015-5-12
i do not understand what u mean with that? rt?
paul kaam
paul kaam 2015-5-12
Now it is between '' with cellstr:
>> S
S =
"12:15",333.98,0.06,0.06,65.3,0.975,0.02,0.10,72.2,1.002,""
>> cellstr(S)
ans =
'"12:15",333.98,0.06,0.06,65.3,0.975,0.02,0.10,72.2,1.002,""'
>> C = textscan(ans, '"%[^"]",%f,%f,%f,%f,%f,%f,%f,%f,%f,%*s', 'CollectOutput', 1); Error using textscan First input must be of type double or string.

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omax ali
omax ali 2020-11-5
i just write this for new ones who searching:
to change some value like a=["1","2.2","3",......] to number format we can do as:
b=char(a);
c=str2num(b);
c gives you the numbers.
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Walter Roberson
Walter Roberson 2020-11-6
编辑：Walter Roberson 2020-11-6
Ran in:
a=["1","2.2","3"]
a = 1×3 string array
"1" "2.2" "3"
double(a)
ans = 1×3
1.0000 2.2000 3.0000
This relies upon a being datatype string and not cell array of character vector:
a = {'1', '2.2', '3'}
a = 1x3 cell array
{'1'} {'2.2'} {'3'}
str2double(a)
ans = 1×3
1.0000 2.2000 3.0000
●

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Philipp Prestel
Philipp Prestel 2023-6-24
编辑：Philipp Prestel 2023-6-24
Ran in:
Again for someone stumbling over this:
if this is your char array: ' "10:58 ", 297.98, 0.25, 0.15, 66.5, 1.194, -0.31, -0.27, 71.1, 0.966,"" '
and these are your values:
val1 (1,1) datetime = 10:58
val2 (1,1) double = 297.98
...
val10 (1,1) double = 0.966
First of all, i want to say something about the array itself; you don't need any qotation marks around the time, it's arbitrary since you already have a char array. Next is the "" at the end, if it is supposed to be a empty string it's fine, otherwise remove it.
This applies if you're indexing stays the same for other arrays you may want to decode, if the indexing varries for some reasons there are better ways of doing dynamic identification.
Generally, I would advise against using char arrays to pass around data. If you have to do it or read from a text file make sure what you save is compatible with sscanf, fscanf, readtable or anything using Matlabs format spec. Json works as well with jsonencode and jsondecode.
if you can't get around it, I found the following to work:
value_char = '"10:58",297.98,0.25,0.15,66.5,1.194,-0.31,-0.27,71.1,0.966,""';
value_char = erase(value_char,'"');
value_cellstr = split(value_char,',');
time_str = string(value_cellstr{1});
value_time = datetime(time_str,InputFormat='HH:mm')
value_time = datetime
24-Jun-2023 10:58:00
num_cellstr = value_cellstr(2:end-1);
nums = cellfun(@str2num,num_cellstr)
nums = 9×1
297.9800 0.2500 0.1500 66.5000 1.1940 -0.3100 -0.2700 71.1000 0.9660
last_str = erase(value_cellstr{end},'"');
last_str = string(last_str)
last_str = ""
This isn't the best implementation but it shows what you can do. Split the array into cell string using ',' as a delimiter then convert the individual cellstirngs to the format you want.
If you want it more adaptive you can also write a small function to use for cellfun, which identifies what type you want a value in and then does the conversion. Which might look something like this:
value_char = '"10:58",297.98,0.25,0.15,66.5,1.194,-0.31,-0.27,71.1,0.966,""';
value_cellstr = split(value_char,',');
nums = cellfun(@convert2type,value_cellstr,UniformOutput=false)
nums = 11×1 cell array
{["10:58" ]} {[297.9800]} {[ 0.2500]} {[ 0.1500]} {[ 66.5000]} {[ 1.1940]} {[ -0.3100]} {[ -0.2700]} {[ 71.1000]} {[ 0.9660]} {["" ]}
function A_convert = convert2type(A)
arguments
A char {mustBeTextScalar}
end
if contains(A,'"')
A_convert = erase(A,'"');
A_convert = string(A_convert);
else
A_convert = str2num(A);
end
end
If you want the time as a datetime just add a condition with ':' to the function in the function.
Bit of along answer but I hope it helps someone having to work with these things.
Edit: By default datetime automatically determines the display format if you only want daytime use Format='preserveinput'

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