# Constraints with for loop and if statements

**URL:** https://discourse.julialang.org/t/constraints-with-for-loop-and-if-statements/45009
**Category:** Optimization (Mathematical)
**Tags:** jump
**Created:** [August 15, 2020, 7:10pm UTC](https://discourse.julialang.org/t/constraints-with-for-loop-and-if-statements/45009 "2020-08-15T19:10:56Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![Micah\_Mungal](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/micah_mungal/32/14660_2.png) [@Micah\_Mungal](https://discourse.julialang.org/u/Micah_Mungal)
#### Post date: [August 15, 2020, 7:10pm UTC](https://discourse.julialang.org/t/constraints-with-for-loop-and-if-statements/45009/1 "2020-08-15T19:10:56Z")

</div>

Hi, I am new to Julia and by extension JuMP. I am trying to rewrite a model for an optimization problem from Matlab to Julia using JuMP. Now following the documentation on the JuMP webpage, I have some doubts about writing the constraints in Julia. In Matlab, one of my constraint looks like this:

```julia
uc_miqp.Constraints.isOn = optimconstr(nHours, nUnits)
for kk = 1:nHours
    for jj = 1:nUnits
        uc_miqp.Constraints.isOn(kk, jj) = isOn(kk, jj) <= 1
    end
end

```

And following the documentation, I have rewritten it as follows:

```julia
@constraint(uc_miqp, [kk = 1:nHours, jj = 1:nUnits], isOn[kk, jj] <= 1)

```

Now I think what I have is correct, but what if I wanted to have it resemble the code in Matlab. Would it look like this:

```julia
for kk = 1:nHours
    for jj = 1:nUnits
        @constraint(uc_miqp, isOn[kk, jj] <= 1)
    end
end

```

Furthermore, I have some constraints with for loops and if else statements. What would be the correct or recommended way to implement something like this? This following is what I have implemented in Julia for for loops containing if else statements. For example if the Matlab code is 🙂

```julia
uc_miqp.Constraints.isOn = optimconstr(nHours, nUnits)
for kk = 1:nHours
    for jj = 1:nUnits
        if kk <= 5
            uc_miqp.Constraints.isOn(kk, jj) = isOn(kk, jj) <= 1
        else
            uc_miqp.Constraints.isOn(kk, jj) = isOn(kk, jj) >= 1
        end
    end
end

```

I have implemented this is in Julia using the following 2 constraints:

```julia
@constraint(uc_miqp, [kk = 1:nHours, jj = 1:nUnits; kk <= 5], isOn[kk, jj] <= 1)
@constraint(uc_miqp, [kk = 1:nHours, jj = 1:nUnits; kk > 5], isOn[kk, jj] >= 1)

```

Would this be the best way to implement this?  
The constraints may not make logical sense, it only used as an example.

---

<div class="post-metadata">

### Author: ![tomerarnon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tomerarnon/32/3170_2.png) [@tomerarnon](https://discourse.julialang.org/u/tomerarnon)
#### Post date: [August 15, 2020, 9:00pm UTC](https://discourse.julialang.org/t/constraints-with-for-loop-and-if-statements/45009/2 "2020-08-15T21:00:27Z")

</div>

> [@Micah\_Mungal](#):
>
> ```julia
> for kk = 1:nHours
> for jj = 1:nUnits
> if kk <= 5
> uc_miqp.Constraints.isOn(kk, jj) = isOn(kk, jj) <= 1
> else
> uc_miqp.Constraints.isOn(kk, jj) = isOn(kk, jj) >= 1
> end
> end
> end
> 
> ```

You can rewrite this to be exactly the same if you want:

```julia
for kk = 1:nHours
    for jj = 1:nUnits
        if kk <= 5
            @constraint(uc_miqp, isOn[kk, jj] <= 0)
        else
            @constraint(uc_miqp, isOn[kk, jj] >= 0)
        end
    end
end

```

Incidentally, you should use `j` and `k` as your loop variables in julia. The convention of `ii, jj, kk` is very ugly, and only born in matlab out of fear of interfering with the imaginary number constants i/j, which is a problem julia doesn’t suffer from.

* * *

For that matter, you can also do:

```julia
@constraint(uc_miqp, isOn[1:5, :] .<= 0)
@constraint(uc_miqp, isOn[6:end, :] .>= 0)

```