How to find first letter of my string is alphabetic??

I have string like "20inputsignal" in this if my string starts with number i need to give some error message how to do this?

expected strings are "in1"--->ok "in20signal1"---->ok but i dont need string starting with number.

for "in1" and "in20signal1" im using reg expression to filter out number both are fine but user should insert those two types only not the "20inputsignal" like string. how to give error condition for this

Answer 1

[Adam]

This works, I think, but I'm sure there are far neater approaches that people will come up with!!

str = "20inputsignal";
ch = char( str );
valid = isnan( str2double( ch(1) ) ) || ~isreal(  str2double( ch(1) ) )

The fact that 'i' is interpreted as 0 + 1i when converted to a double adds more complexity than I at first thought!

Answer 2

[Kevin Chng]

let say

a = "in1"
check = all(ismember(a(1), '0123456789'));

if check is 1, then it is not okay, else vice versa.

[shivaraj c]

for this method if i am checking a="in1" it is giving check=1 it should give 0 write

[shivaraj c]

i need numbers after my first character is alphabetic but i dont need string with starting numeric

[Adam]

You need to convert the string to a char if you are using a(1) as a string like that is a scalar representing the whole string rather than a char array where you can index each character.

[Kevin Chng]

a = "in1"
b = char(a)
check = all(ismember(b(1), '0123456789'));