See the following definition of your class. This uses vectorized operations, which make the code simple, faster, and more readable. Also, there is no need to use if-condition for each case, as did in your code.
% WIP
classdef Datum
properties
Value
Variance
end
methods
function obj = Datum(Val_ini, Var_ini)
% Following allow faster initialization. See here: https://blogs.mathworks.com/loren/2012/03/26/considering-performance-in-object-oriented-matlab-code/
if nargin > 0
for i = numel(Val_ini):-1:1
obj(i).Value = Val_ini(i);
obj(i).Variance = Var_ini(i);
end
end
end
function r = plus(a, b)
if isa(a, 'Datum') && isa(b, 'Datum')
r = Datum(a.value + b.value, a.variance + b.variance);
elseif isa(a, 'Datum')
r = Datum(a.value + b, a.variance);
else % only when b is Datum
r = Datum(a + b.value, b.variance);
end
end
function r = minus(a, b)
r = plus(a, -1 * b);
end
function r = mtimes(a, b)
% matlab's automatically making everything matrices all the
% time is a disaster
if isa(a, 'Datum') && isa(b, 'Datum')
r = Datum(a.value .* b.value, a.value.^2 .* b.variance + a.variance .* b.value.^2);
elseif isa(a, 'Datum')
r = Datum(a.value * b, b^2 * a.variance);
else
r = Datum(a * b.value, a^2 * b.variance);
end
end
function r = mpower(a, b)
if isa(a, 'Datum')
r = Datum(a.value.^b, b^2 * a.value.^(2*b-2) .* a.variance);
elseif isa(b, 'Datum')
r = Datum(a.^b.value, log(a)^2 * a.^(2 * v.value) .* b.variance);
end
end
function r = mrdivide(a, b)
r = mtimes(a, b^-1);
end
function r = rdivide(a, b)
r = arrayfun(@mrdivide, a, b);
end
function r = log(a)
r = Datum(log(a.value), a.variance ./ a.value);
end
function r = exp(a)
r = Datum(exp(a.value), exp(2 * a.value .* a.variance));
end
function r = variance(a)
r = [a.Variance];
end
function r = stdev(a)
r = sqrt([a.Variance]);
end
function r = value(a)
r = [a.Value];
end
end
end
Few test cases
x1 = Datum(1:10, zeros(1, 10)); % 1 x 10 Datum
x2 = Datum(2*ones(1, 10), 2*ones(1,10)); % 1 x 10 Datum
x3 = Datum(1, 3); % 1 x 1 Datum
y1 = 2 + x1;
y2 = x2 - 3;
y3 = x1 + x2;
y4 = x2 - x1;
y5 = x1 - x3;
y6 = x1 * x2;
y7 = x1 * x3;
y8 = 2 * x1;
y9 = x1 * 5;
