Define multiple variables efficiently - matlab

Question

Is there a way to define multiple variables efficiently in matlab? Everything I've found isn't quite what I'm looking for. Here's the situation:
parstrs = {'a','b','c'};
parvals = [1 2 3];
I want an efficient command which would in effect do the following;
parstrs = parvals;
where the result is that the number 1 is stored in the variable a, 2 is stored in b, and 3 is stored in c, etc.
I'm open to doing this with cells or structs.
Any suggestions?
More clarification: As I mention below, I would like to write code that doesn't care how long the list of variable names is for use in curve fitting. The best way I've discovered is to use a structure, like the following:
parstrs = {'a','b','c'};
parvals = num2cell([1 2 3]);
partmp = {parstrs{:};parvals{:}};
pars = struct(partmp{:});
The problem with this is that the pars structure can't be edited in the same way. That is,
pars = setfield(pars,partmp{:});
will throw the following error:
Error using setfield (line 48)
Inputs must be either cell arrays or strings.

Answer 1

You're looking for eval, but that would probably still require a loop (yes you could generate a lengthy command, but do you really want that?):
Loop (please do not use this!):
for ii=1:numel(parvals)
eval([parstrs(ii) '=parvals(' ii ')']);
end
eval is most of the time totally not needed and discouraged; changing to cells is much easier to manage and use. You already have the variables in a vector, what's the problem with just using indexing to inspect them?
You should explain your application a bit more, so we can understand what you're really after, why you really want to use this kind of variable assignment.
For exporting variables outside from a gui to the base matlab environment, you can switch to evalin, and use it as follows:
function main_gui()
% do your thing, generate some values
parvals = [1 2 3];
% now is the time to export
give_me_my_vars({'a','b','c'});
% note that the following function is nested:
function give_me_my_vars(parstrs)
for ii=1:numel(parvals)
evalin('base',[parstrs(ii) '=' parvals(ii)]);
end
end
end
This is only possible for simple scalars, which fit in a string. I think you actually want to look for something to switch variables from one workspace to another (gui to base), but I don't know if that'd be possible.

Answer 2

You could use
parstrs = {'a','b','c'};
parvals = {'1' '2' '3'};
cellfun(#(x,y)evalin('caller', [x '=' y]), parstrs, parvals)
Alternatively, you could do something like
parstrs = {'a','b','c'};
parvals = {1 2 3};
parstrs = cellfun(#(x)[x ','], parstrs, 'UniformOutput', false);
eval(['[' parstrs{:} '] = deal(parvals{:});'])
However, as MATLAB's code analyzer will already complain about, this is a bit smelly. Usually, mass-defining variables using eval and friends is a sign you should think about a different approach.
For example, why do you even want to be able to address the values by separate variable name? Why is parvals(1), parvals(2) etc. not good enough?

Answer 3

You can create a structure with field names from parstrs with values taken from parvals like so:
parstrs = {'a', 'b', 'c'};
parvals = [1 2 3];
nValues = length(parvals);
for iValue = 1:nValues
s.(parstrs{iValue}) = parvals(iValue);
end
The structure, s, then looks like this:
s =
a: 1
b: 2
c: 3
So instead of a = 1, you'd have s.a = 1, but I think it's otherwise what you were after.

Answer 4

You could do something like:
[a, b] = function_returning_values();
You can also use eval.

Answer 5

Most of the chances that you can store the values in a single array:
x = [1 2 3];
Then, instead of writing a , write x(1) , instead of b write x(2), etc...

Answer 6

How about something like [a,b,c] = deal(1,2,3)? Or am I oversimplifying?