Symbols instead of line with plot

Hi, wanted to know why appears some symbols instead of the line with plot.

This is what I get:

And this is some part of the code:

function temp_Callback(hObject, eventdata, handles)
global s;
% hObject    handle to temp (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'Value') returns position of slider
%        get(hObject,'Min') and get(hObject,'Max') to determine range of slider
T = get(hObject, 'Value'); %get value from slider
set(handles.text15, 'String', T); %Set the slider's value to the static text

[k,Cp]=proptermicas(T,s); %k y cp are calculated sending as parameters the slider value and the substance

set(handles.edit8, 'String', k); %Set the k to the edit box
set(handles.edit7, 'String', Cp); %Set Cp to the last edit box

cla()
T_ = linspace(-50,400,20); %Declare a new variable with the slider range -50 to 400

for i = 1:20 %for i to linespace 20
    [k,Cp]=proptermicas(T_(i),s); %call to the function
    k_ = k;
    Cp_ = Cp;
end

yyaxis left
cla
plot(T_,k_)
hold on
plot(T,k,'kx', 'LineWidth',2)  

yyaxis right
plot(T_,Cp_)
hold on
plot(T,Cp,'kx', 'LineWidth',2)  

[Walter Roberson]

I predict that proptermicas is returning a character such as '^' rather than numbers.

Answer 1

[the cyclist]

It looks like it might be because

k_

is only a single value, the last one of the loop. Maybe you wanted

k_(i) = k;

in the loop?

[Walter Roberson]

Oh, could be... the change in symbols might be due to the "hold on", which I did not pay attention to when I commented.