From char to number

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

Answer 1

[Robbin van Hoek]

try str2num!

>> str2num('6.1')

ans =

    6.1000

[paul kaam]

but it is of type char, if i do str2num i get the result : ans = [ ]

Answer 2

[Walter Roberson]

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};

[paul kaam]

S is of type char, so is get the following error:

Error using textscan

First input must be of type double or string.

if it was of typ str it would work!

[Walter Roberson]

A string is a char array, not a different datatype.

I tested the code, so if you copy and paste it, it should work

[paul kaam]

true it works! Thanks.. but this is what i get:

S = fgetl(board)

S =

"12:11",43.00,-0.05,0.00,64.4,0.918,0.04,-0.22,73.4,0.989,""

>> C = textscan(S, '"%[^"]",%f,%f,%f,%f,%f,%f,%f,%f,%f,%*s', 'CollectOutput', 1); Caught "std::exception" Exception message is: invalid string position

greets

[Walter Roberson]

When I assign that text into a string it works. I deduce that there must be some extra invisible characters. Please run again and when it errors out, show both S (the visible string) and

S+0

which will show the character codes associated with each string position

[paul kaam]

S = fgetl(board)

S =

"12:15",323.98,0.06,0.07,64.5,0.997,0.04,0.03,72.2,1.001,""

>> C = textscan(S, '"%[^"]",%f,%f,%f,%f,%f,%f,%f,%f,%f,%*s', 'CollectOutput', 1); Caught "std::exception" Exception message is: invalid string position

>> S

S =

"12:15",323.98,0.06,0.07,64.5,0.997,0.04,0.03,72.2,1.001,""

>> S+0

ans =

Columns 1 through 13

    34    49    50    58    49    53    34    44    51    50    51    46    57

Columns 14 through 26

    56    44    48    46    48    54    44    48    46    48    55    44    54

Columns 27 through 39

    52    46    53    44    48    46    57    57    55    44    48    46    48

Columns 40 through 52

    52    44    48    46    48    51    44    55    50    46    50    44    49

Columns 53 through 60

    46    48    48    49    44    34    34    13

[Walter Roberson]

You did not open the file with 'rt' to read in text mode.

[Walter Roberson]

That is, the carriage return on the end was telling textscan that there was another line to process with the format, but then there was no text to process so the match against '"' could not take place.

[paul kaam]

i do not understand what u mean with that? rt?

[paul kaam]

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.

Answer 3

[omax ali]

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.

[Walter Roberson]

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

●

Answer 4

[Philipp Prestel]

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'