Temperature vs time plot

I want to plot data vs temperature data from an external file:

fileID_A=fopen('discesa_salita.txt');  
 A = textscan(fileID_A,'%D %s');
 time_A=A{1}; 
  time=time_A(37:210) ;
 temp_A=A{2}; 
  temp=temp_A(37:210) ; 

figure()
  plot(time, temp);

But Matlab said: "Error using plot Invalid second data argument", what am I doing wrong?

[KSSV]

What is class of temp and time? What are their sizes?

[Michela Longhi]

they are

00:00:00  26
00:00:01  26
00:00:02  26
00:00:03  26
00:00:04  26
00:00:05  26

[KSSV]

Class of time? class(time) gives what output? You need to convert it to certain format to plot.

[Michela Longhi]

I don't know... how can I convert to seconds, for example?

Answer 1

[KSSV]

time = {'00:00:00'
'00:00:01'  
'00:00:02'
'00:00:03'
'00:00:04'
'00:00:05'} ;

temp = [26 ; 26 ; 26;26;26;26] ;

plot(second(time),temp) ;

Answer 2

[Peter Perkins]

You are likely to be much happier using readtable than textscan. Given that you've used '%D %s' as the format, your temperatures are read in as a cell array of char vectors, and plot isn't going to like that.

Try something like this:

t = readtable('discesa_salita.txt','ReadVariableNames',false); % best guess
t.Var1 - timeofday(t.Var1); % timestamps read as datetimes, convert to durations
t = t(37:210,:);
plot(time, temp);

Depending on what version of MATLAB, you may need to give readtable a format.