MATLAB: I can’t plot a line with the function??

lineplot

As shown below, my function can only plot dots instead of solid lines, do anyone knows why? Thank you
 %Finding indoor temperature
 function [dTin] = getTin_00(Tin)            %Input of function should be Tin = 5 and Theater = 40 normally
 dt =0.1;
 m = 4.9;
 Tout = 5;
 Theater = 40;
 M = 0.25;
 c = 1005.4;
 Ar = 2.8197;
 Aw = 10.2042;
 Uwall = 0.0069;
 Uroof = 0.0179; 
 dQheater = (Theater-Tin)*M*c*dt;
 dQloss = (Tin-Tout)*Ar*Uroof*dt+(Tin-Tout)*Aw*Uwall*dt;
 dTin = (dQheater - dQloss)/(m*c);                            
 for t = 0:0.1:200        %increment 0.1 is equal to dt
    dQheater = (Theater-Tin)*M*c*dt;
    dQloss = (Tin-Tout)*Ar*Uroof*dt+(Tin-Tout)*Aw*Uwall*dt;
    dTin = (dQheater - dQloss)/(m*c);
    Tin = Tin+dTin;
    if Tin <= 21
        Theater = 40;
    end
    if Tin >= 24
        Theater = 0;
    end
    figure(1);
    plot(t,Tin,'.r');
    title('The change in temperature over 200 seconds');   
    xlabel('Time'); 
    ylabel('Internal temperature');
    hold on;
    grid on;
    axis tight;
    disp(Tin)
 end
 end

Best Answer

As Stephen pointed out, you are only plotting one point at a time, therefore the can't join to form a line. One way is to assign all the values in a vector and then plot it at the end of the loop. As an alternate approach, you can use line handle object to dynamically draw as in the following example
function [dTin] = getTin_00(Tin)            %Input of function should be Tin = 5 and Theater = 40 normally
dt =0.1;
m = 4.9;
Tout = 5;
Theater = 40;
M = 0.25;
c = 1005.4;
Ar = 2.8197;
Aw = 10.2042;
Uwall = 0.0069;
Uroof = 0.0179;
dQheater = (Theater-Tin)*M*c*dt;
dQloss = (Tin-Tout)*Ar*Uroof*dt+(Tin-Tout)*Aw*Uwall*dt;
dTin = (dQheater - dQloss)/(m*c);
p = plot(0,0,'r');
p.XData = [];
p.YData = [];
title('The change in temperature over 200 seconds');
xlabel('Time');
ylabel('Internal temperature');
grid on
axis tight;
for t = 0:0.1:200        %increment 0.1 is equal to dt
  dQheater = (Theater-Tin)*M*c*dt;
  dQloss = (Tin-Tout)*Ar*Uroof*dt+(Tin-Tout)*Aw*Uwall*dt;
  dTin = (dQheater - dQloss)/(m*c);
  Tin = Tin+dTin;
  if Tin <= 21
      Theater = 40;
  end
  if Tin >= 24
      Theater = 0;
  end
  p.XData = [p.XData t];
  p.YData = [p.YData Tin];   
  disp(Tin)
end
end
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