How do I make a while loop that will return to a statement unless a condition is met

I am trying to make a while loop that will goes on forever unless a condition is met, in this case I want the loop to keep repeating unless I enter the word imperial or metric. And when I enter other words it will continue ask the question "Please make a choice", the code i have here just opts out whenever i enter other words

clear,clc

x = [];

while isempty(x)

    x = input('Please make a choice (imperial or metric) - ','s');

    if strcmp(x,'imperial')

        disp('yes')

    if strcmp(x,'metric')

            disp('no')

    end

    end

Answer 1

[Walter Roberson]

If strcmp()
  ...
elseif strcmp()
  ...
else
 Give message
 x = '' 
end

[Quan Seah]

I tried your answer it seems like i still get the same problem when i enter words other than imperial and metric, it just opts out of the loop

[Walter Roberson]

Please show your revised code