# how to compare previous and next values in MATLAB?

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zehra ülgen on 6 Nov 2020
Commented: Jon on 9 Nov 2020
Write a function called number_pattern that takes no input arguments and returns no output arguments. Instead it gets it input via the function input. It asks for a number repeatedly until the user puts in the same number twice in a row. The loop that it uses must be a while-loop. Here is an example run:
>> matching_number
Please input a number: 4
Please input number (I'm looking for a pattern): 5
Sorry, that's not what I'm looking for.
Please input number (I'm looking for a pattern): 6
Sorry, that's not what I'm looking for.
Please input number (I'm looking for a pattern): 7
Sorry, that's not what I'm looking for.
Please input number (I'm looking for a pattern): 7
That's it. Well done!
The function should behave just as in the example, using exactly the same phrasing in its output (e.g., “That’s it. Well done!”)
I tried to write code but I did not understand how can I compare previous "b" and next "b". Here is my code..
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zehra ülgen on 6 Nov 2020
function number_patter
a = input ('Please input a number: ');
while 1
b = input ('Please input number (I''m looking for a pattern): ');
if a == b
fprintf('That''s it. Well done!\n');
return;
elseif b == b
fprintf('That''s it. Well done!\n');
return;
else
fprintf('Sorry, that''s not what I''m looking for.\n');
end
end
zehra ülgen on 6 Nov 2020
'number repeatedly until the user puts in the same number twice in a row'
to do that statement I should compare the previous 'b value' and new 'b value'. But when I said b == b my code is not working. How can I compare last two b value?

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### Accepted Answer

Mathieu NOE on 7 Nov 2020
hi
I believe this works :
function number_patter
b = [];
a = input ('Please input a number: ');
while 1
b = input ('Please input number (I''m looking for a pattern): ');
if a == b
fprintf('That''s it. Well done!\n');
return;
elseif b == prev_b
fprintf('That''s it. Well done!\n');
return;
else
fprintf('Sorry, that''s not what I''m looking for.\n');
end
prev_b = b;
end
##### 2 CommentsShow NoneHide None
zehra ülgen on 8 Nov 2020
I'm sorry it's nor working..
>> number_pattern
Please input a number: 4
Please input number (I'm looking for a pattern): 5
Unrecognized function or variable 'prev_b'.
Error in number_pattern (line 9)
elseif b == prev_b
But if I change the prev_b = b; like that.. Code is working.. Thank you very much for your helps..
function number_patter
b = [];
a = input ('Please input a number: ');
while 1
prev_b = b;
b = input ('Please input number (I''m looking for a pattern): ');
if a == b
fprintf('That''s it. Well done!\n');
return;
elseif b == prev_b
fprintf('That''s it. Well done!\n');
return;
else
fprintf('Sorry, that''s not what I''m looking for.\n');
end
end
Mathieu NOE on 8 Nov 2020
yes better this way ! :)

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### More Answers (1)

Jon on 6 Nov 2020
You need to create a new variable, call it for example prevB. After each loop set
prevB = B
when you do your comparison compare prevB and B
Note you will need to initialize prevB before entering the loop so it is defined the first time through. Just set it to something that the user would never enter for example prevB = inf
##### 2 CommentsShow NoneHide None
zehra ülgen on 6 Nov 2020
I'm not sure I got you right but I tried to do something and it is not working again..
function number_patter
a = input ('Please input a number: ');
prevB = input ('Please input number (I''m looking for a pattern): ');
while 1
b = input ('Please input number (I''m looking for a pattern): ');
if b == a
fprintf('That''s it. Well done!\n');
break;
elseif b == prevB
fprintf('That''s it. Well done!\n');
break;
else
fprintf('Sorry, that''s not what I''m looking for.\n');
end
end
Jon on 9 Nov 2020
You need to assign prevB = b insinde of the loop

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