Questions Tagged With variablehttp://www.or-exchange.com/tags/variable/?type=rssquestions tagged <span class="tag">variable</span>enTue, 17 Oct 2017 14:35:50 -0400Simulate Binary Variable in Linear Programming for Decision Variablehttp://www.or-exchange.com/questions/15102/simulate-binary-variable-in-linear-programming-for-decision-variable<p>I want to simulate a binary variable (Y) within a linear program
I am trying something similar to BigM, but I call this LittleM.
This is what I am trying:</p>
<p>Y - 0.01 <= 0 + 0.01 * ( 1 - Y )
0.99 - Y <= 0 + 0.01 * Y
Y - 1.01 <= 0 + 0.01 * Y
Y <= 1.01</p>
<p>The first equation is TRUE when Y = 0.005, and the other two are FALSE.
The second and third equations are TRUE when Y = 0.995, and the first equation is FALSE.</p>
<p>This is saying that either Y <= 0.01 or ( Y >= 0.99 and Y <= 1.01 )</p>
<p>I am using a tolerance of 0.01</p>
<p>This does not work in the LP solver. Any suggestions on how to implement this? </p>
<p>This would allow anyone the ability to use LP solvers to solve MILP.</p>
<p>Regards,
Fulton Loebel</p>fultonTue, 17 Oct 2017 14:35:50 -0400http://www.or-exchange.com/questions/15102/simulate-binary-variable-in-linear-programming-for-decision-variablevariabledecisionprogramminglinearsimulateLinearize equality constraint with binary variablehttp://www.or-exchange.com/questions/12581/linearize-equality-constraint-with-binary-variable<p>I have an equality constraint like z(Ax-y)=0, where z>=0 ,and x is binary variable, and y is bounded variable Lx<=y<=Ux. How can it be linearized? Thanks in advance.</p>zunTue, 07 Jul 2015 16:58:40 -0400http://www.or-exchange.com/questions/12581/linearize-equality-constraint-with-binary-variablelinearizationbinaryvariableequalityconstraintGet integer value for a variable without IPhttp://www.or-exchange.com/questions/11505/get-integer-value-for-a-variable-without-ip<p>I have a variable Wmn[m,n,t] and I want the AMPL to solve it as an integer without defining it as integer.</p>ZaidFri, 27 Feb 2015 18:17:01 -0500http://www.or-exchange.com/questions/11505/get-integer-value-for-a-variable-without-ipvariableintegerReciprocal Normal distribution?http://www.or-exchange.com/questions/10215/reciprocal-normal-distribution<p>Hello all,</p>
<p>I have a question about random variable.
I want to estimate or approximately estimate the probability distribution of travel time based on the velocity.
If the velocity follows normal distribution, travel time = distance / velocity.
The distance is constant and velocity is random variable.
Then the travel time should be random variable.
Can I say the travel time also approximately follows normal distribution?
And if possible, can I use the mean of the travel time as distance / E(Velocity)?
Thanks in advance.</p>GitaeWed, 24 Sep 2014 07:26:32 -0400http://www.or-exchange.com/questions/10215/reciprocal-normal-distributionvariablerandomOnly one variable get valuehttp://www.or-exchange.com/questions/8983/only-one-variable-get-value<p>Dear OR experts,</p>
<p>I have this equation in my model:</p>
<p>X_it + Y_it - Z_it - N_i = 0 where all of these variables are continues. The problem is that Y_it and Z_it cannot have values greater than zero in the same time step (t). In other words, if Y_it is greater than zero, Z_it has to be zero and vise versa.</p>
<p>Could you please give me your idea about how to formulate this condition in my model.</p>
<p>Thanks</p>
<p>Kam</p>KamFri, 03 Jan 2014 04:27:18 -0500http://www.or-exchange.com/questions/8983/only-one-variable-get-valuevariablehow to make my constraint solvable in cplex?http://www.or-exchange.com/questions/6258/how-to-make-my-constraint-solvable-in-cplex<p>I don't know how deal with following constraint:
x(m,h)=t(m,h)*[1-t(m,m+1)]*[1-t(m,m+2)]*...[1-t(m,h-1)], of which t() are all boolean variables.
Such as x(1,7)=t(1,7)*[1-t(1,2)][1-t(1,3)]...*[1-t(1,6)]</p>
<p>A model including such a constraint can not be solved by cplex. So I want to ask can you help me to make a change to the constraint so that it can be extracted by cplex.</p>
<p>Thank you.</p>XimenesTue, 21 Aug 2012 22:58:57 -0400http://www.or-exchange.com/questions/6258/how-to-make-my-constraint-solvable-in-cplexvariablecplexconstraint