Not enough input arguments

I am new to Matlab and I am currently getting a problem that I do not have enough input arguments.

The code is as follows:

function P = Antoine(T,A,B,C) % vapour pressure [bar]
T = input('Temperature of water in degrees celcius = ')
T_k = 273.15 + T;
P = 10^(A - (B/(T_k + C))); % temperature [K]

if (0 < T) & (T <= 30)

      A = 5.40221;
      B = 1838.675;
      C = -31.737;
  end
  if (30 < T) & (T <= 60)

      A = 5.20389;
      B = 1733.926;
      C = -39.485;
  end
  if (60 < T) & (T <= 90)

      A = 5.0768;
      B = 1659.793;
      C = -45.854;
  end 
  end

Answer 1

[madhan ravi]

function P = Antoine(T,A,B,C) % vapour pressure [bar]
T = input('Temperature of water in degrees celcius = ')
T_k = 273.15 + T;

if (0 < T) & (T <= 30)
      A = 5.40221;
      B = 1838.675;
      C = -31.737;
      P = 10^(A - (B/(T_k + C))); % temperature [K]

    elseif (30 < T) & (T <= 60)
        A = 5.20389;
        B = 1733.926;
        C = -39.485;
        P = 10^(A - (B/(T_k + C))); % temperature [K]

    elseif (60 < T) & (T <= 90)
        A = 5.0768;
        B = 1659.793;
        C = -45.854;
        P = 10^(A - (B/(T_k + C))); % temperature [K]
    end 
    end

[madhan ravi]

If it’s what you are looking for please accept the answer, if not let know.

[Walter Roberson]

The same formula is used for P each time in the code, so you might as well put the P calculation after the if tree.

However, be careful: if the use enters a non-positive T or a T > 90, then the code does not assign a value to P (or to the coefficients needed to calculate P)

[madhan ravi]

Thank you sir , the reason I put P in each tree is that I thought it might reduce the computational time.

Answer 2

[Basil C.]

The code you have written is correct all that you need to do is to define the variable P after you have defined the value of A,B,C,T (that is at the end of the if statements)

Also no need to use function P = Antoine(T,A,B,C) rather use function P = Antoine() as the arguments that are passed are not used to compute the value of P as they get overwritten

 function P = Antoine() % vapour pressure [bar]
T = input('Temperature of water in degrees celcius = ');
T_k = 273.15 + T;
if (0 < T && T <= 30)

      A = 5.40221;
      B = 1838.675;
      C = -31.737;
  end
  if (30 < T && T <= 60)

      A = 5.20389;
      B = 1733.926;
      C = -39.485;
  end
  if (60 < T && T <= 90)

      A = 5.0768;
      B = 1659.793;
      C = -45.854;
  end 
  P = 10^(A - (B/(T_k + C))); % temperature [K]
  end