Terminate while loop when user hits enter

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klb
klb 2021-4-10
评论： klb 2021-4-12
Hi eveyone,
This is my while loop. It must end when user hits enter without entering a value . The loop allows for upto 3 successive blank entries before terminating. And, I cant get the n_points matrix to save entries without error.
How do I fix these?
Thank you for your time.
clear all
disp('Begin entering the data points')
t = 1;
x_point = input('enter x : ')
y_point = input('enter y : ')
n_points = [x_point,y_point];
while x_point ~= isempty(x_point) | y_point ~= isempty(y_point) % does not terminate immedeately when user presses enter without entering a value.
x_point = input('enter x : ')
y_point = input('enter y : ')
t = t+1
n_points(t,:) = [x_point,y_point];
end

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采纳的回答

Jan
Jan 2021-4-11
编辑：Jan 2021-4-11
Avoid repeating code:
disp('Begin entering the data points')
t = 0;
while true % Infinite loop
x_point = input('enter x : ');
if isempty(x_point)
break; % Stop the WHILE loop
end
y_point = input('enter y : ');
if isempty(y_point)
break; % Stop the WHILE loop
end
t = t + 1;
n_points(t, :) = [x_point, y_point];
end
Or:
disp('Begin entering the data points')
t = 0;
ready = false;
while ~ready
x_point = input('enter x : ');
if ~isempty(x_point)
y_point = input('enter y : ');
end
if ~isempty(x_point) && ~isempty(y_point)
t = t + 1;
n_points(t, :) = [x_point, y_point];
else
ready = true;
end
end
  1 个评论
klb
klb 2021-4-12
Thanks Jan, this works. Much aprpeciate the two different while loop logics. With these, you have clarified the following as well.
For some reason I have been under the impresison that the loop terminating logic must only be provided at the start of loop, and statements in the loop run till that logic returns a false. I see now that a while loop can be terminated from inside the loop as well. Thank you!

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更多回答（1 个）

Jonathan Clayton
Jonathan Clayton 2021-4-10
the code below looks at the number of elements that the user has inputed for that loop, and if that number is zero then the loop is broken.
if numel(x_point)+numel(y_point)==0
break
end
Add this code above n_points variable so that the empty vaibles are not added to your list.
  4 个评论
显示 2更早的评论
klb
klb 2021-4-11
编辑：klb 2021-4-11
Incorporated your code block as seen in code below. If you run it, skipping x is ok. But skipping y value copies the x value to y. If I add your code a second time with if numel(y_points)==0 edit, It works , but that is blunt.
A while loop shouldnt need further fixes. That is my original question - how to terminate the While loop at the very first time user hits enter without having adding data.
clear all
disp('Begin entering the data points')
t = 1;
x_point = input('enter x : ')
y_point = input('enter y : ')
n_points = [x_point,y_point];
while x_point ~= isempty(x_point) | y_point ~= isempty(y_point)
x_point = input('enter x : ')
y_point = input('enter y : ')
if numel(x_point)==0
break
end
t = t+1
n_points(t,:) = [x_point,y_point];
end
I tried another logic here but it also needs 2 of those code blocks. Cant understand why doesnt the loop break with the main while loop conditon itself. Any suggestions to eliminate in-loop intemedeate conditions checks?
clear all
t=0;
x_point = 0;
y_point = 0;
while numel(x_point)~= 0
x_point = input('enter x : ')
y_point = input('enter y : ')
if numel(x_point)==0
break
end
if numel(y_point)==0
break
end
t = t+1;
n_points(t,:) = [x_point,y_point]
end
n_points
klb
klb 2021-4-12
Jonathan, I am using the code block. I am also learning its ok to terminate a while loop from the inside the loop. Thanks for your time and help!

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