isblank.m

Determines if the argument string consists only of blanks.

Description

Function determines whether the string str consists only of blank characters. For strings of blank characters function returns logical 1. For empty strings function returns logical 0. For non-character arguments function returns a type mismatch error.

Examples:
>> isblank(' ')
ans =
1
>> isblank(' foo ')
ans =
0

• MATLAB release: MATLAB 7.10 (2010a)

[Oleg Komarov]

Help and H1 line may be improved. No examples. No history.

Fails if matrix char:
x = [' '
      ' '];

Also I would rather go for all(isspace(x))) even though my timings indicate that isblank can be ?faster?

The main engine can be simplified:
x = all(x==blanks(length(x)));

Oleg

[janez]

thanks for your comments oleg. they were very useful and also my timings indicate all(isspace(x)) solution is most of the time 1.5-2 times faster than isblank and the x = all(x==blanks(length(x))) solution is about 20% faster.

i also noticed my complicated code is sometimes faster - how is that possible indeed? but good point there too: speedwise my code is the worst most of the time.

i'm sure it's clear from this which solution to use ;) but i'll keep my file posted anyway for pedagogical purposes - i don't want to extinguish your comment.

[Jan Simon]

You can omit the call of BLANKS:
  x = all(x==blanks(length(x)));
Faster (does not overwrite x, considers matrices):
  y = all(x(:)==' ');
But ISSPACE catchs other invisible characters also:
  y = all(x(:) <= ' '); % or <= 32
Because all characters with ASCII < 33 are invisible.

[Binbin Qi]

I think the main engine can be simplified:
                    x=length(deblank(x))==0

[Binbin Qi]

also, all(x==' ')
           all(isspace(x))