Entering numbers from the keyboard

I want to input 4 numbers from the keyboard, then have the m file give me the largest and second largest numbers.

How do I check that the input is a number (and not a letter/other character) and how do I get the second largest number to be shown?

Also the programme should run continuously, taking 4 numbers at a time until the user wants to terminate, eg with an 'N' , how do I do this?

Thanks in advance

[Azzi Abdelmalek]

What have you done so far? specify the problems you have encountered

[Brian]

xvalueone = 'enter a value for x';
xvalue = input(xvalueone);
a=xvalue

xvaluetwo = 'enter another value for x';
xvaluetwo = input(xvaluetwo);
b=xvaluetwo

xvaluethree = 'enter a third value for x';
xvaluethree = input(xvaluethree);
c=xvaluethree

xvaluefour = 'enter a 4th value for x';
xvaluefour = input(xvaluefour);
d=xvaluefour

A=[a,b,c,d]
C = max(A)

I don't know how to only allow input from numbers, how to keep the programme running until I terminate it or how to terminate it.

Thanks

Answer 1

[Image Analyst]

Start with this:

% Ask user for 4 numbers.
defaultValues = {'1', '2', '3', '4'};
titleBar = 'Enter values';
userPrompts = {'Enter number #1', 'Enter number #2', 'Enter number #3', 'Enter number #4'};
% Loop until user clicks Cancel
while true
  caUserInput = inputdlg(userPrompts, titleBar, 1, defaultValues);
  if isempty(caUserInput),break,end; % Bail out if they clicked Cancel.
  [value1, value2, value3, value4] = caUserInput{:}
  value1 = str2double(value1)
  value2 = str2double(value2)
  value3 = str2double(value3)
  value4 = str2double(value4)
  
  % Check for a valid number.
  if isnan(value1)
    % They didn't enter a number.
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    message = sprintf('value1 is not a number.\nI said it had to be an number.');
    uiwait(warndlg(message));
  end
  if isnan(value2)
    % They didn't enter a number.
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    message = sprintf('value2 is not a number.\nI said it had to be an number.');
    uiwait(warndlg(message));
  end
  if isnan(value3)
    % They didn't enter a number.
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    message = sprintf('value3 is not a number.\nI said it had to be an number.');
    uiwait(warndlg(message));
  end
  if isnan(value4)
    % They didn't enter a number.
    % They clicked Cancel, or entered a character, symbols, or something else not allowed.
    message = sprintf('value4 is not a number.\nI said it had to be an number.');
    uiwait(warndlg(message));
  end
end

Answer 2

[Azzi Abdelmalek]

for k=1:4
  xvalue='';
  while ~isnumeric(xvalue)
      test=0;
      text=sprintf('enter a value  n°%d for x',k);
      str=input(text,'s');
      id=regexp(str,'\d*\.?\d*','match')
      if isempty(id)
          id={' '};
          test=1;
      end
      if numel(id{:})==numel(str) & test==0 & ~isequal(str,'.')
          xvalue=str2num(str)
      else
          xvalue=''
      end
  end
  A(k)=xvalue
end
c=max(A)

[Brian]

I tried to get the second max number but could not, this is what I have:

for k=1:4
xvalue='';
while ~isnumeric(xvalue)
    test=0;
    text=sprintf('enter a value  n°%d for x',k);
    str=input(text,'s');
    id=regexp(str,'\d*\.?\d*','match')
    if isempty(id)
        id={' '};
        test=1;
    end
    if numel(id{:})==numel(str) & test==0 & ~isequal(str,'.')
        xvalue=str2num(str)
    else
        xvalue=''
    end
end
A(k)=xvalue
end
c=max(A)

c = max(A);
Y = A(A ~= c);
b = max(Y);

Also how do I make the programme run over and over again until a special input is entered?

Thanks

[Image Analyst]

Why not just get all 4 numbers in one single call to inputdlg() like I showed you?

[Azzi Abdelmalek]

c = max(A);
Y = A(A ~= c);
b = max(Y);

is correct

you can also do

y=unique(sort(A))
c=y(end)
b=y(end-1)

I did'nt understand : make the programme run over and over again until a special input is entered

[Brian]

I originally used the code which gets all four in one go, however I couldn't make it keep rejecting answers until a number is entered

the best I could do was keep copying the second bit so it would reject a few times.

by this "make the programme run over and over again until a special input is entered" I mean I want it to keep asking for sets of 4 numbers and returning the highest and second highest in the array until the user decides to terminate the programme

[Image Analyst]

All you have to do is put my code in a while loop. When you click Cancel it exits. See my answer - I edited it to add the while.

[Azzi Abdelmalek]

ask='enter 4 values: press 1 to quit  any other key to continue'
q=input(ask,'s');
while ~isequal(q,'1')
  for k=1:4
      xvalue='';
      while ~isnumeric(xvalue)
          test=0;
          text=sprintf('enter a value  n°%d for x',k);
          str=input(text,'s');
          id=regexp(str,'\d*\.?\d*','match');
          if isempty(id)
              id={' '};
              test=1;
          end
          if numel(id{:})==numel(str) & test==0 & ~isequal(str,'.')
              xvalue=str2num(str);
          else
              xvalue='';
          end
      end
      A(k)=xvalue;
  end
  y=unique(sort(A));
  c=y(end)
  b=y(end-1)
  q=input(ask,'s');
end

[Brian]

The requirements are to also have the loop terminate when the letter "n" is inputted into any of the four boxes:

This is what I have now, mainly based on the original code from image analyst.

Tried to implement an if command for the termination by "n" but failed.

 defaultValues = {'1', '2', '3', '4'};
titleBar = 'Enter values';
userPrompts = {'Enter number #1', 'Enter number #2', 'Enter number #3', 'Enter number #4'};

while true caUserInput = inputdlg(userPrompts, titleBar, 1, defaultValues); if isempty(caUserInput),break,end; [value1, value2, value3, value4] = caUserInput{:} value1 = str2double(value1) value2 = str2double(value2) value3 = str2double(value3) value4 = str2double(value4)

if isnan(value1) message = sprintf('value1 is not a number.\nI said it had to be an number.'); uiwait(warndlg(message)); end if isnan(value2) message = sprintf('value2 is not a number.\nI said it had to be an number.'); uiwait(warndlg(message)); end if isnan(value3) message = sprintf('value3 is not a number.\nI said it had to be an number.'); uiwait(warndlg(message)); end if isnan(value4) message = sprintf('value4 is not a number.\nI said it had to be an number.'); uiwait(warndlg(message)); end

end

a = [value1 value2 value3 value4] maxnumberis = max(a(:))

b=sort(a(:),'descend'); disp(b'); secondmaxnumber= b(2,1)

[Image Analyst]

Please fix the formatting so we can copy and paste it.