How to optimize some functions?

Hey guys,

So, I need to found the minimun values of Z and W when my parameters [pmax, pmin, td, tm] = [57086.00, 15420.247, 0.002026].

Restrictions: 0.2<=Z<= 39 and W>=0.1

Can you help me? I really don't know how can I optmizete those functions. Suggestion of command in matlab?

Thank you!

% Input Data
% Z    = 5;
% W    = 10;

% Positive Phase

if (0.07071 < Z && Z <= 0.1895)
    pmax = 1000000 * 26.303 * Z^(-1.226);
elseif (0.1895 < Z && Z <= 0.48735)
    pmax = 1000000 * 13.015 * Z^(-1.637);
elseif (0.48735 < Z && Z <= 1.096)
    pmax = 1000000 * 8.1 * Z^(-2.322);
elseif (1.096 < Z && Z <= 2.418)
    pmax = 1000000 * 8.0956 * Z^(-2.943);
elseif (2.418 < Z && Z <= 5.442)
    pmax = 1000000 * 4.9419 * Z^(-2.427);
elseif (5.442 < Z)
    pmax = 1000000 * 0.8645 * Z^(-1.411);
end
% ----------------------------------------------------------------------- % 

% Negative Phase

if (Z <= 0.7)
    A = 0; B = 0; C = 0; D = 100E-3;
elseif (Z > 0.7) && (Z <= 1.469)
    A = -29.078E-3; B = 2; C = 0.0352E-3; D = 114E-3;
elseif (Z > 1.469) && (Z <= 2.754)
    A = 84.132E-3; B = -1.286; C = 0; D = 0;
elseif (Z > 2.754)
    A = 59.559E-3; B = -0.945; C = 0; D = 0;
end

pmin = double(10^6 * (( A * ( Z ^ B ) )...
    + ( C * Z ) + D));
% ----------------------------------------------------------------------- %

% Positive Time

if (0.20993 < Z && Z <= 1.0355)
    td = 0.001 * ( 2.2064 * Z^3 - 0.3363 * Z^2 - ...
        0.5644 * Z + 0.3756 ) * ( W^(1/3) );
elseif (1.0355 < Z && Z <= 1.49339)
    td = 0.001 * ( 8.2395 * Z^3 - 34.896 * Z^2 + ...
        48.909 * Z - 20.496 ) * ( W^(1/3) );
elseif (1.49339 < Z && Z <= 4.001)
    td = 0.001 * ( -0.2695 * Z^3 + 2.3907 * Z^2 - ...
        6.1005 * Z + 6.8329 ) * ( W^(1/3) );
elseif (4.001 < Z)
    td = 0.001 * ( 1.5602 * log(Z) +1.2416 ) * ...
        ( W^(1/3) );
end
% ----------------------------------------------------------------------- % 

% Negative Time

if (0.0717 < Z && Z <= 0.1985)
    id = 1000 * ( 0.4352 * Z^( -1.949 ) ) * ...
        ( W^(1/3) );
elseif (0.1985 < Z && Z <= 1.2895)
    id = 1000 * ( 0.8709 * Z^( -1.501 ) ) * ...
        ( W^(1/3) );
elseif (1.2895 < Z)
    id = 1000 * ( 0.7805 * Z^( -1.104 ) ) * ...
        ( W^(1/3) );
end

% disp(['    Peak reflect overpressure   = ' num2str(pmax) ' Pa']);
% disp(['    Peak reflect subpressure    = ' num2str(pmin) ' Pa']);
% disp(['    Time of positive phase      = ' num2str(td) ' s']);
% disp(['    Impulse of positive phase   = ' num2str(id) ' Pa.s']);