How to convert string to variable name which will be passed into plot function - matlab

Question

How I can convert a string to a variable which will be passed into plot function?
Time = [0,1,2,3];
A = sin(Time);
B = cos(Time);
c = 2*sin(Time);
lookup = {"A", "Freq(Hz)"; "B", "Pressure(bar)", "c", "time(ms),....};
for i=1:length(lookup)
plot(Time, lookup(i,1))
ylabel(lookup(i,2))
end
I want to plot Time vs A and Time vs B and Time vs C likewise I have 50 different variables to plot.
So I planned to create the lookup with string and planned to pass as variable to plot function using eval function call.
But in few places I read that using eval is not good option so kindly suggest the alternate method.

Answer 1

This will solve your immediate problem:
Replace
lookup = {"A", "Freq(Hz)"; "B", "Pressure(bar)", "c", "time(ms)", ...};
with
lookup = {A, "Freq(Hz)"; B, "Pressure(bar)", c, "time(ms)", ...};
Cell arrays are heterogeneous containers, each element can be an array of any time, independently from all other types.
With this change, the rest of your code should work as intended. You might want to add a figure command or a print command inside your loop, as each plot will overwrite the previous one. figure creates a new figure window to plot in, you'll have 50 windows (not so nice). print can save the plot to a file, which might be a better approach here. Don't try to combine the 50 data lines into a single plot, it'll be a mess!
On a larger scale, you might want to rethink your strategy with defining 50 different variables. Cell arrays and struct arrays are really good ways to go about this. For example, you can think of
data.A = sin(Time);
data.B = cos(Time);
data.c = 2*sin(Time);
or
data(1).values = sin(Time);
data(1).name = "A";
data(1).units = "Freq(Hz)";
data(2).values = cos(Time);
data(2).name = "B";
data(2).units = "Pressure(bar)";
data(3).values = 2*sin(Time);
data(3).name = "c";
data(3).units = "time(ms)";
Note that, in the first case, you can also index with data.("A"), which brings you pretty close to your original idea, except that you don't have 50 variables in your workspace, but one single data structure that is easier to deal with.
Here is a very detailed list of reasons why eval can be bad to use. That link also shows some alternatives, similar to what I summarized above.