Former behaviour of ~NaNs (of interest to Matlab users from mid-90s)

Hallo

I am running (for the first time since I wrote it) a Matlab script from 1996. In it I have a line where

a = ~b;

where b contains some NaNs. This used to run, but now, with the advent of the logical type, it won't accept ~NaN;

>> ~NaN Error using ~ NaN's cannot be converted to logicals.

But what was the value of ~NaN in those days? was it 0 or 1?

Thanks

Answer 1

[Jan]

1996 sounds like Matlab 4.2c or 5.0. In these times logical 's have been double 's with an extra flag. This has been change in 6.5.

I assume, that ~NaN has been NaN, even as logical type. But in the documentation I find "TRUE is everything but 0". I will try this in the evening with Matlab 5.3.

[EDITED: after running a test in Matlab 5.3]:

a = ~NaN;
disp(a)
%  >> 0
class(a)
%  >> double
islogical(a)
%  >> 1

Therefore I assume this is required for your program:

b(isnan(b)) = 1;  % Anything but 0
a = ~b;