Re: how to convert a structure array of strings into a string array?

[Bob Odom]

How about:

octave:1> a=["eins"; "zwei"; "drei"]
a =

eins
zwei
drei


On Fri, 17 Oct 2008, Thorsten Meyer wrote:

> Hi,
>
> I would like to convert a large structure array of strings into a string
> array in a nicely vectorized way.
>
> for example:
> octave:15> a={"eins", "zwei", "drei"};
>
> should be converted into
> ans =
>
> eins
> zwei
> drei
>
> =================================================
> My first attempt was:
>
>
> octave:16> a{:}
> ans =
>
> (,
>  [1] = eins
>  [2] = zwei
>  [3] = drei
> ,)
> Very nice: this generates a list of strings.
>
> octave:17> [a{:}]
> ans = einszweidrei
> Here, the elements of the list are concatenated in the wrong way. :-(
> =================================================
>
> The cat function can concatenate correctly:
>
> octave:69> cat(1, a{:})
> ans =
>
> eins
> zwei
> drei
>
> However, it is incredibly slow for larger arrays and it cannot handle
> strings of different length.
> =================================================
>
> This works, but I suppose it's rather slow for large arrays (also it is
> not robust if the strings contains things like "):
> octave:28> eval(["[", sprintf("""%s"";", a{:}), "]"])
> ans =
>
> eins
> zwei
> drei
>
> =================================================
>
> then there is the str2mat function that does the trick:
> octave:14> str2mat(a{:})
> ans =
>
> eins
> zwei
> drei
>
> However, looking at its source, it is only a loop over the list of input
> strings. Trying with a large array
>         a=cellstr(char(70+floor(20*rand(50000,100))));
> the eval solution takes 5s, while the str2mat function takes 11.3s on my
> computer (the cat function caused my octave to hang for that example).
>
> Does anyone has a better idea?
>
> thanks and regards
>
>
> Thorsten Meyer
>
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