They are not random characters at all, they are in fact exactly the characters with exactly those character codes that you specified (most of the ones you generated are non-printing control characters):
"I can't seem to find a reason why,"
When you concatenate a character vector and a numeric MATLAB does not implicitly convert the numeric values into a string representing the values stored in the numeric: it converts the numeric into the characters whose codes are given by those numeric values. For example:
>> X = 'A';
>> X(2) = 4 % this does NOT create the character vector 'A4' !
X =
A
>> double(X) % check the character codes:
ans =
65 4
You can use num2str or sprintf to convert numerics to character arrays representing the numeric values, e,g.:
>> strcat('50HZ',cellstr(num2str((1:54).')))
ans =
'50HZ 1'
'50HZ 2'
'50HZ 3'
'50HZ 4'
'50HZ 5'
'50HZ 6'
'50HZ 7'
'50HZ 8'
'50HZ 9'
'50HZ10'
'50HZ11'
'50HZ12'
'50HZ13'
'50HZ14'
'50HZ15'
'50HZ16'
'50HZ17'
'50HZ18'
'50HZ19'
'50HZ20'
'50HZ21'
'50HZ22'
'50HZ23'
'50HZ24'
'50HZ25'
'50HZ26'
'50HZ27'
'50HZ28'
'50HZ29'
'50HZ30'
'50HZ31'
'50HZ32'
'50HZ33'
'50HZ34'
'50HZ35'
'50HZ36'
'50HZ37'
'50HZ38'
'50HZ39'
'50HZ40'
'50HZ41'
'50HZ42'
'50HZ43'
'50HZ44'
'50HZ45'
'50HZ46'
'50HZ47'
'50HZ48'
'50HZ49'
'50HZ50'
'50HZ51'
'50HZ52'
'50HZ53'
'50HZ54'
