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<p>Ana,</p>
<p> I think you can do it using boolean functions, which return a 1
when the condition is true and a 0 when the condition is false.
GT(x,y) will return a 1 if x>y. GE(x,y) will return a 1 if
x>=y. <br>
</p>
<p>I didn't try it out to be sure but I think you can write the
following four equations:<br>
</p>
<p>cond1 = AND(GT(x,-57),LT(x,-30))</p>
<p>cond2 = AND(GE(x,-30),LT(x,-15))</p>
<p>cond3 = AND(GE(x,-15),LE(x,-5))</p>
<p>Y = cond1*(8E-5x**2-0.0024+0.2385) +
cond2*(0.0001x**2+0.0028x+0.3494) +
cond3*(-0.0001x**2-0.004x+0.3058)</p>
<p>best,</p>
<p> David</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 07/19/2022 04:52, Ana Delgado via
TRNSYS-users wrote:<br>
</div>
<blockquote type="cite"
cite="mid:PA4PR02MB663780257482809A5283DE67E48F9@PA4PR02MB6637.eurprd02.prod.outlook.com">
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<p class="MsoNormal">Hello, </p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have an input variable that changes over
time. The most correct way to characterize it is to use a
branch function. I wanted to use the equations feature but it
is giving me lots of errors. Using programming language, my
variable changes like this:</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If -57 < x < -30<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Y1=8E-5x^2-0.0024+0.2385<o:p></o:p></p>
<p class="MsoNormal">End IF<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If -30< x<-15<o:p></o:p></p>
<p class="MsoNormal">Y2=0.0001x^2+0.0028x+0.3494<o:p></o:p></p>
<p class="MsoNormal">End if<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If -15< x<-5<o:p></o:p></p>
<p class="MsoNormal">Y3=-0.0001x^2-0.004x+0.3058<o:p></o:p></p>
<p class="MsoNormal">End if <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Do you have any tip on how to do it on
TRNSYS? Also it’s not mandatory to use equations.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you in advance, <o:p></o:p></p>
<p class="MsoNormal">Kind Regards, <o:p></o:p></p>
<p class="MsoNormal"> Ana Delgado, University of Aveiro <o:p></o:p></p>
</div>
<br>
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<pre class="moz-signature" cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy System Specialists, LLC
3 North Pinckney Street - suite 202
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P:+1.608.274.2577
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