Re: FindRoot::nlnum error message for non-linear system of equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg57067] Re: [mg57042] FindRoot::nlnum error message for non-linear system of equations*From*: Chris Chiasson <chris.chiasson at gmail.com>*Date*: Sat, 14 May 2005 04:58:04 -0400 (EDT)*References*: <200505130244.WAA23978@smc.vnet.net>*Reply-to*: Chris Chiasson <chris.chiasson at gmail.com>*Sender*: owner-wri-mathgroup at wolfram.com

Here is a guess: Unprotect Short and Set it to Identity. Run your code again and see if the function value (lhs-rhs) is a list of numbers. Verify that Dimension returns {39} from that list. On 5/12/05, daniel.chung at yale.edu <daniel.chung at yale.edu> wrote: > Hello, > I have recently started using Mathematica and I've been using it to > solve non-linear systems of equations via the FindRoot command. I am > using it to solve approximations of building airflow and when I had a > relatively small system of 6 equations and 6 unknowns I had no problem > getting it to solve for the unknowns. More recently though I have been > trying to solve a system of 39 equations with 39 unknowns and I've been > running into error messages. I've tried changing the format of the > start values to include a range but I still get a FindRoot::nlnum error > message. Any help would be appreciated. > -Daniel Chung, daniel.chung at yale.edu > > Here is the text for the input followed by the generated error message: > > Clear[ > (* Variables - 39 unknowns *) > m14, m23, m33, m11, m24, m21, m42,m31, m44, m83, m51, m61, > m64, m54, m63, m53, > v1,v2,v3,v4,v5,v6, v7, > p1,p2,p3,p4,p41, p42, p43, p44, p45, p46, p5, p54, p57, > p6, p66, p67 > ]; > (* Constants *) > ro = 1.2; > A1= 0.0099; A2 = 0.0300; A3 = 0.0200; A4 = 0.0250; > A5 =0.0300; A6 =0.0300; A7 = 0.0250; > ev1 = 2.4; ev2 = 2.4; ev3 =2.4; ev5 =2.4; ev6 =2.4; ev7 = 2.4; > K14 = 0.00373; K23 = 0.00328; K33 = 0.00319; K53 = 0.00310; > K63 = 0.00152; K83 = 0.00190; K11 = 0.00389; > K21 = 0.00562; K24 = 0.0000472; K31 = 0.00415; > K42 = 0.000825; > K44 = 0.00157; K51 = 0.00418; K54 = 0.00175; > K61 = 0.000344; K64 = 0.000553; > n14 = 0.58; n23 = 0.60; n33 = 0.58; n53 = 0.54; n63 = 0.56; > n83 = 0.59; n11 = 0.90; n21 = 0.78; n24 = 0.87; n31 = > 0.59; > n42 = 0.65; n44 = 0.51; n51 = 0.76; n54 = 0.64; n61 = 0.81; > n64 = 0.69; > (* Boundary Conditions *) > pow = 16; > pol = -81; > pos = -2.8; > results=FindRoot [ > { m14-m11-ro*v3*A3 ==0, > m11+m23-m21-m24-ro*v1*A1==0, > m24+m33+m42-m31-ro*v2*A2==0, > m21+m31-m14-m44-m51-m61+ro*v1*A1+ro*v2*A2+ro*v3*A3-ro*v4*A4- > ro*v5*A5-ro*v6*A6==0, > m44+m51+m54-m53+ro*v4*A4+ro*v7*A7==0, > m61+m64-m54-m63+ro*v6*A6-ro*v7*A7==0, > m14-ro*K14*(pow-p1)^n14 == 0, > m23-ro*K23*(pow-p2)^n23 == 0, > m33-ro*K33*(pow-p3)^n33 == 0, > m11-ro*K11*(p1-p2)^n11 == 0, > m24-ro*K24*(p2-p3)^n24 == 0, > m21-ro*K21*(p2-p4)^n21 == 0, > m42-ro*K42*(p4-p3)^n42 == 0, > m31-ro*K31*(p3-p4)^n31 == 0, > m44-ro*K44*(p4-p5)^n44 == 0, > m83-ro*K83*(p4-pos)^n83 == 0, > m51-ro*K51*(p4-p5)^n51 == 0, > m61-ro*K61*(p4-p6)^n61 == 0, > m64-ro*K64*(pos-p6)^n64 == 0, > m54-ro*K54*(p6-p5)^n54 == 0, > m63-ro*K63*(p6-pol)^n63 == 0, > m53-ro*K53*(p5-pol)^n53 == 0, > p2*v1*A1-0.5*ro*(v1^3)*A1*ev1-p41*v1*A1 == 0, > p3*v2*A2-0.5*ro*(v2^3)*A2*ev2-p42*v2*A2 == 0, > p1*v3*A3-0.5*ro*(v3^3)*A3*ev3-p43*v3*A3 == 0, > p44*v4*A4-0.5*ro*(v4^3)*A4*ev4-p54*v4*A4 == 0, > p45*v5*A5-0.5*ro*(v5^3)*A5*ev5-pos*v5*A5 == 0, > p46*v6*A6-0.5*ro*(v6^3)*A6*ev6-p66*v6*A6 == 0, > p67*v7*A7-0.5*ro*(v7^3)*A7*ev7-p57*v7*A7 == 0, > (p41*v1*A1+0.5*ro*(v1^3)*A1)+(p42*v2*A2+0.5*ro*(v2^3)*A2)+ > (p43*v3*A3+0.5*ro*(v3^3)*A3) - > (p45*v5*A5+0.5*ro*(v5^3)*A5) - > (p46*v6*A6+0.5*ro*(v6^3)*A6) - > (p44*v4*A4+0.5*ro*(v4^3)*A4) == 0, > p41-p42 == 0, > p41-p43 == 0, > p41-p44 ==0, > p41-p45 == 0, > p4-p41 == 0, > p5-p54 == 0, > p5-p57 == 0, > p6-p66 == 0, > p6-p67 == 0 > }, > (* Initial Guesses *) > {m14,0.0125}, {m23,0.0106}, {m33,0.0233}, {m11,0.001}, > {m24,0.002}, {m21,0.003}, {m42,0.004}, {m31,0.005}, {m44,0.006}, > {m83,0.007}, {m51,0.008}, {m61,0.009}, {m64,0.01}, {m54,0.011}, > {m63,0.0103}, {m53,0.0186}, {v1,0.90},{v2,0.63},{v3,0.60}, > {v4,0.33},{v5,0.54},{v6,0.52}, {v7,0.22},{p1,14.},{p2,12.}, > {p3,10.},{p4,0.},{p41,0.1},{p42,0.2},{p43,0.3},{p44,0.4}, > {p45,0.5},{p46,0.6},{p5,-20.},{p54,-20.1},{p57,-20.2},{p6,-30.}, > {p66,-30.1},{p67,-30.2} > ]; > > ColumnForm[results] > > FindRoot::nlnum: The function value {-0.0029, -0.004092, 0.00162, - > 0.027788, 0.0229, 0.00982, 0.00580905, <<28>>, > 0.1, 0.2, 0.1, 0.2} is not a list of numbers with dimensions {39} at > {m14, m23, m33, m11, m24, m21, m42, m31, m44, m83, m51, m61, <<21>>, > p5, p54, p57, p6, p66, p67} = > {0.0125, 0.0106, 0.0233, 0.001, 0.002, 0.003, 0.004, 0.005, <<27>>, - > 20.2, -30., -30.1, -30.2}. More.. > > -- Chris Chiasson http://chrischiasson.com/ 1 (810) 265-3161

**References**:**FindRoot::nlnum error message for non-linear system of equations***From:*daniel.chung@yale.edu