problem with 'extract' function

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Damian Maxwell
Damian Maxwell on 30 Jan 2021
Commented: dpb on 3 Feb 2021
I am trying to extract characters from a string at a specific position using the 'extract' function.
However, even when entering the example code into my matlab program I get the error
Undefined function 'extract' for input arguments of type 'string'.
Can somebody help with this?
Matlab help page:
Section: Extract Character at Numeric Position
Create a string.
str = "All's well that ends well"
Extract the first character in the string.
extract(str,1)
From the command window:
>> str = "All's well that ends well"
str =
"All's well that ends well"
>> extract(str,1)
Undefined function 'extract' for input arguments of type 'string'.
Thanks!

Answers (2)

Star Strider
Star Strider on 30 Jan 2021
The extract function was introduced in R2020b. If you have an earlier version/release, you need to upgrade to be able to use it. If you have R2020b and are still unable to use extract, run these commands:
restoredefaultpath
rehash toolboxcache
from a script or your Command Window and then try running it again. If you are still having problems after that, Contact Support.
  2 Comments
Damian Maxwell
Damian Maxwell on 3 Feb 2021
I'll try to upgrade from my 2019 version

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dpb
dpb on 30 Jan 2021
What do you get when you type
ver
at command line?
extract wasn't introduced until just now in R2020b so if you have a release earlier than that, you'll either have to upgrade or use the {} notation to get to the underlying char() string inside the string class string...
>> str = "All's well that ends well"
Extract the first character in the string.
extract(str,1)
str =
"All's well that ends well"
Unrecognized function or variable 'Extract'.
>> str{:}(1)
ans =
'A'
>>
  2 Comments
dpb
dpb on 3 Feb 2021
That was the only way to extract a substring from a string variable prior to R2020b that released extract into the wild.

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