Problems with DO and TABLE...

*To*: mathgroup at smc.vnet.net*Subject*: [mg2092] Problems with DO and TABLE...*From*: lfreitas at ift.unesp.br (Luciene Pontes Freitas)*Date*: Fri, 29 Sep 1995 01:14:31 -0400

Dear Wizards, I've been tried to evaluate a function I've been called B[n,t,x] with fixed n,x and the parameter 'a', and the variable t in the range [t1,t2] with a step st. I tried to do that using two different methods: 1) The Do command, as you can see in the function P[x,t,t1,t2,st]; 2) Using a Table, as showed in the function P1[n_,x_,t1_,t2_,st_]. The results I've been found were: *********** RESULTS *************** In[2]:= a:=3.1 In[3]:= P[4,.7,1,2,.2] B1[4,1,0.7] = {0.79 Second, 0.758841} B1[4,1.2,0.7] = {0.79 Second, 1.33161} B1[4,1.4,0.7] = {0.79 Second, 2.49627} B1[4,1.6,0.7] = {0.79 Second, 4.97146} B1[4,1.8,0.7] = {0.78 Second, 10.4205} B1[4,2.,0.7] = {0.78 Second, 22.7483} In[9]:= P1[4,.7,1,2,.2] Out[9]= {{0.79 Second, 0.758841}, {0.79 Second, 1.33161}, {0.79 Second, 2.49627}, {0.8 Second, 4.97146}, {0.79 Second,10.4205}, {0.78 Second, 22.7483}} ****************************************** But if I calculate the function B[n,t,x] for each t in the same points I've done to the functions P[...] and P1[...] the results are different of those ones. Example: In[3]:= B1[4,1,0.7] Out[3]= {0.85 Second, 0.651} In[4]:= B1[4,1.6,0.7] Out[4]= {0.84 Second, 0.841106} Which problem could be happening in this calculation? I'm sure the results above (given by B1[...]) are right. Thanks in advance Luciene. ********* The definitions used ****************************** x[j_]:=-a^(-j); Pro[n_,x_,t_]:=Product[(1+t*x[i]),{i,n}]; Sigma[n_,j_]:=Coefficient[Pro[n,x,t],t,j]; (Zigmund[n_,k_,i_]:=Sum[(a^(i*j))*Sigma[n,j],{j,0,k-1}]); (Funct[n_,i_]:=Sum[Zigmund[n,k,i],{k,1,n}]); (Ro[n_,i_,k_]:=Sum[(a^(i*(j-k)))*Sigma[n,j],{j,0,k-1}]/Funct[n,i]); (Coef[n_,k_,t_]:=Sum[Ro[n,i,k]*a^(i*t),{i,1,n}]); g[x_]:=a*x*(1-x); " defining a value to variable 'a', example a:=3.1 " a:=3.1 B1[n_,t_,x_]:=Timing[Sum[Coef[n,k,t]*Nest[g,x,k],{k,1,n}]]; P[n_,x_,t1_,t2_,st_]:=Do[Print["B1[",n,",",t,",",x,"]"," = ", B1[n,t,x]],{t,t1,t2,st}]; P1[n_,x_,t1_,t2_,st_]:=Table[B1[n,t,x],{t,t1,t2,st}] ***************************************************************