No curve in plot when executing function with multiple data sets

So I have a function to output a value of heat capacity for a given species and temperature.

function[c]=HeatCapacity(Species,T)
if Species == 1
    a = 38.91; b = 3.903e-2; c = -3.105e-5; d = 8.606e-9;
    Cp = [d c b a];
    HeatCapacity = polyval(Cp,T)
end
if Species == 2
    a = 48.50; b = 9.188e-2; c = -8.540e-5; d = 32.40e-9;
    Cp = [d c b a];
    HeatCapacity = polyval(Cp,T)
end
if Species == 3
    a = 29.10; b = 1.158e-2; c = -0.607e-5; d = 1.311e-9;
    Cp = [d c b a];
    HeatCapacity = polyval(Cp,T)
end
if Species == 4
    a = 29.00; b = 0.2199e-2; c = -0.5723e-5; d = -2.871e-9;
    Cp = [d c b a];
    HeatCapacity = polyval(Cp,T)
end
% Cp = a + b*T + c*T^2 + d*T^3

And so I want to write a script that plots dependencies of heat capacity for all four species versus temperature in the temperature range ‐100ºC <= T <= 1000ºC in a single plot

for Species = 1:4
    T = -100:1:1000
    HeatCapacity(Species,T);
    plot(T,HeatCapacity(Species,T))
    xlim([-100,1000])
    ylim([0,100])
end

However this returns a blank plot with no curves. How can I fix this in order to display the four curves?

Answer 1

[Jyotsna Talluri]

The function output variable should be initialized same as the passing variable . For plotting multiple plots on the same curve use hold on and hold off

function Capacity = HeatCapacity(Species,T) 
if Species == 1 
    a = 38.91; b = 3.903e-2; c = -3.105e-5; d = 8.606e-9; 
    Cp = [d c b a]; 
    Capacity = polyval(Cp,T) 
    end 
if Species == 2 
    a = 48.50; b = 9.188e-2; c = -8.540e-5; d = 32.40e-9; 
    Cp = [d c b a]; 
    Capacity = polyval(Cp,T) 
end 
if Species == 3 
    a = 29.10; b = 1.158e-2; c = -0.607e-5; d = 1.311e-9; 
    Cp = [d c b a]; 
    Capacity = polyval(Cp,T) 
end 
if Species == 4 
    a = 29.00; b = 0.2199e-2; c = -0.5723e-5; d = -2.871e-9; 
    Cp = [d c b a]; 
    Capacity = polyval(Cp,T) 
end 
end
figure(); 
hold on; 
for Species = 1:4 
    T = -100:1:1000 
    c=HeatCapacity(Species,T); 
    plot(T,c) 
  
    xlim([-100,1000]) 
    ylim([0,100]) 
end 
hold off