MATLAB: IF statement with multiple logical OR

if or multiple plot

I'm running a function that solves a given PDE using Euler's method
I attempt to plot the numerical solutions to the PDE at specific times (0.1, 0.5, 1.0 and 2.0) by testing equalities for t in an IF statement
However, only plots for t == 0.1 and t == 0.5 are plotted for some reason
I've tried debugging with breakpoints and the IF statement tests true when t == 0.1 and 0.5, but false when t == 1 and 2, even though the variable t in the workspace == 1 and 2
The relevant code is:
t = 0;
dt = 0.1;
for a = 1 : timesteps
      for b = 1 : nodes
          u = %solve PDE;
      end
      t = t + dt;
      round(t,1);
      if t == 0.1 || t ==0.5 || t == 1.0 || t == 2.0
          figure
          plot(t,u)
      end
  end

Best Answer

This line does not perform ynathing, because theoutput is not stored:
round(t,1);
You cannot expect, that 0.1+0.1+0.1 is exactly 0.3, because the most decimal floating point values do not have an exact representation in the binary system, such that rounding errors occur.
Better use an arbitrary, but matching threshold:
if any(abs(t - [0.1, 0.5, 1.0. 2.0]) < 1e8)
   figure
   plot(t,u)
end
Add a meaningful comment to explain the size of the threshold.
Since R2015a:
if ismembertol(t, [0.1, 0.5, 1.0. 2.0])
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