gasState.m

function [p,s,r,e,a,h,t]=gasState(t,r,p,e,s,h)

% INPUTS (in specific order): 
%             temperature, t
%             density, r
%             pressure, p
%             energy, e
%             entropy, s
%             enthalpy, h
% only two of these inputs are expected to be non-zero. An error will occur if this is not the case. 
% Example function call: [p,s,r,e,a,h,t]=gasState(0,0,2549,0,7623.8,0)
%                           this will calcualte all properties using pressure and entropy
%
% OUTPUTS (in specific order): 
%             pressure, p
%             entropy, s
%             density, r
%             energy, e
%             speed of sound, a
%             enthalpy, h
%             temperature, t    
%% units
unitsin=1; %input('\nAre your input units SI(1) or British(2)?\n');
unitsout=1; %input('\nDo you want your output in SI(1) or British units(2)?\n');

if unitsin==2
    % British to SI
      p=p*6894.747;
      r=r*16.01846;
      t=t/1.8;
      e=e*2325.965;
      h=h*2325.965;
      s=s*(1.8*2325.965);   
end
brk=0;
%%
% Given "Pressure, Entropy" (p,s)
if t==0 && r==0 && e==0 && h==0
    r=r_ps(p,s);
    a=a_ps(p,s);
    e=e_ps(p,s);
    t=t_pr(p,r);
    h=e+p/r;
    
% Given "Energy, Density" (e,r)
elseif t==0 && p==0 && s==0 && h==0
    [p,a]=pa_er(e,r,1);
    s=s_re(r,e);
    t=t_pr(p,r);
    h=e+p/r;
    a=a_ps(p,s);
    
% Given "Pressure, Density" (p,r)
elseif t==0 && e==0 && s==0 && h==0
    h=h_pr(p,r);
    t=t_pr(p,r);
    e=h-p/r;
    s=s_re(r,e);
    a=a_ps(p,s);
    
% Given "Entropy, Enthalpy" (s,h)
elseif t==0 && e==0 && p==0 && r==0
    [p,e,r]=per_hs(h,s);
    t=t_pr(p,r);
    a=a_ps(p,s);
    
% Given "Pressure, Temperature" (p,t)
elseif r==0 && e==0 && s==0 && h==0  
    r=r_pt(p,t);
    h=h_pr(p,r);
	e=h-p/r;
    s=s_re(r,e);
    a=a_ps(p,s);
else
    fprintf('\n\nERROR:\nYou must enter only 2 variables, all others must be zero. \n')
    fprintf('Also, the pair of variables MUST be one of the following combinations:\n')
    fprintf('(p,t)\n(p,r)\n(s,h)\n(e,r)\n(p,s)\n')
    brk=1;
end

%% units
if unitsout==2 && brk==0
    % SI to British
      p=p/6894.747;
      r=r/16.01846;
      t=t*1.8;
      e=e/2325.965;
      h=h/2325.965;
      s=s/(1.8*2325.965);
      a=a/0.3048;
end
if brk==1
      p=p/6894.747;
      r=r/16.01846;
      t=t*1.8;
      e=e/2325.965;
      h=h/2325.965;
      s=s/(1.8*2325.965);
      a=0;
end
end