Unable to understand how FindFit function works.

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ks = 0.01, 1, 2, 4, 6, 8, 10, 25, 50, 100, 200, 300, 400, 500, 600, 
 800, 1*^3, 2*^3, 4*^3, 5*^3, 10*^3, 15*^3, 20*^3, 30*^3, 40*^3, 
 70*^3, 1*^5, 1*^6, 1*^8, 1*^12;
aa1 = 3.14172, 3.15756, 3.17331, 3.2041, 3.23399, 3.26304, 3.29131, 
 3.48223, 3.74135, 4.13211, 4.66617, 5.04019, 5.3278, 5.56008, 
 5.75347, 6.05965, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314;
aa2 = 9.42478, 9.42537, 9.42596, 9.42716, 9.42836, 9.42955, 9.43075, 
 9.43974, 9.45479, 9.48511, 9.54657, 9.60893, 9.67202, 9.73563, 
 9.79957, 9.92774, 10.0553, 10.6536, 11.5696, 11.9059, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663;
aa3 = 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.9037, 
 13.3636, 13.6161, 13.8784, 14.0112, 14.1813, 14.2487, 14.388, 
 14.4031, 14.4032;
p1 = ListLogLinearPlot[Table[ks[[i]], aa1[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p2 = ListLogLinearPlot[Table[ks[[i]], aa2[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p3 = ListLogLinearPlot[Table[ks[[i]], aa3[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
Show[p1, p2, p3, PlotRange -> All]
lst = N[Table[Log10[ks[[i]]], aa1, i, Length[ks]]]
model = a E^(b (x - c))/(E^(b (x - c)) + 1) + d
ff = FindFit[lst, model, a, b, c, d, x]
Plot[model /. ff, x, 0, 12, PlotRange -> 0, 12, 3, 6.5, 
 GridLines -> Automatic]

I have three sets of data aa1,aa2,aa3, I am trying to fit an equation for this data, data looks like a sigmoid function. So I have used a fit model which resembles the sigmoid function. Later I used the FindFit function to extract the unknown coefficients. when I plotted the fitted model I am getting a straight line. What mistake I am doing. same thing is happening for aa2 and aa3.

fitting

share|improve this question

asked 7 hours ago

vijay

1357

add a comment | 

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ks = 0.01, 1, 2, 4, 6, 8, 10, 25, 50, 100, 200, 300, 400, 500, 600, 
 800, 1*^3, 2*^3, 4*^3, 5*^3, 10*^3, 15*^3, 20*^3, 30*^3, 40*^3, 
 70*^3, 1*^5, 1*^6, 1*^8, 1*^12;
aa1 = 3.14172, 3.15756, 3.17331, 3.2041, 3.23399, 3.26304, 3.29131, 
 3.48223, 3.74135, 4.13211, 4.66617, 5.04019, 5.3278, 5.56008, 
 5.75347, 6.05965, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314;
aa2 = 9.42478, 9.42537, 9.42596, 9.42716, 9.42836, 9.42955, 9.43075, 
 9.43974, 9.45479, 9.48511, 9.54657, 9.60893, 9.67202, 9.73563, 
 9.79957, 9.92774, 10.0553, 10.6536, 11.5696, 11.9059, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663;
aa3 = 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.9037, 
 13.3636, 13.6161, 13.8784, 14.0112, 14.1813, 14.2487, 14.388, 
 14.4031, 14.4032;
p1 = ListLogLinearPlot[Table[ks[[i]], aa1[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p2 = ListLogLinearPlot[Table[ks[[i]], aa2[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p3 = ListLogLinearPlot[Table[ks[[i]], aa3[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
Show[p1, p2, p3, PlotRange -> All]
lst = N[Table[Log10[ks[[i]]], aa1, i, Length[ks]]]
model = a E^(b (x - c))/(E^(b (x - c)) + 1) + d
ff = FindFit[lst, model, a, b, c, d, x]
Plot[model /. ff, x, 0, 12, PlotRange -> 0, 12, 3, 6.5, 
 GridLines -> Automatic]

I have three sets of data aa1,aa2,aa3, I am trying to fit an equation for this data, data looks like a sigmoid function. So I have used a fit model which resembles the sigmoid function. Later I used the FindFit function to extract the unknown coefficients. when I plotted the fitted model I am getting a straight line. What mistake I am doing. same thing is happening for aa2 and aa3.

fitting

share|improve this question

asked 7 hours ago

vijay

1357

add a comment | 

up vote
1
down vote

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1

up vote
1
down vote

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1

ks = 0.01, 1, 2, 4, 6, 8, 10, 25, 50, 100, 200, 300, 400, 500, 600, 
 800, 1*^3, 2*^3, 4*^3, 5*^3, 10*^3, 15*^3, 20*^3, 30*^3, 40*^3, 
 70*^3, 1*^5, 1*^6, 1*^8, 1*^12;
aa1 = 3.14172, 3.15756, 3.17331, 3.2041, 3.23399, 3.26304, 3.29131, 
 3.48223, 3.74135, 4.13211, 4.66617, 5.04019, 5.3278, 5.56008, 
 5.75347, 6.05965, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314;
aa2 = 9.42478, 9.42537, 9.42596, 9.42716, 9.42836, 9.42955, 9.43075, 
 9.43974, 9.45479, 9.48511, 9.54657, 9.60893, 9.67202, 9.73563, 
 9.79957, 9.92774, 10.0553, 10.6536, 11.5696, 11.9059, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663;
aa3 = 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.9037, 
 13.3636, 13.6161, 13.8784, 14.0112, 14.1813, 14.2487, 14.388, 
 14.4031, 14.4032;
p1 = ListLogLinearPlot[Table[ks[[i]], aa1[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p2 = ListLogLinearPlot[Table[ks[[i]], aa2[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p3 = ListLogLinearPlot[Table[ks[[i]], aa3[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
Show[p1, p2, p3, PlotRange -> All]
lst = N[Table[Log10[ks[[i]]], aa1, i, Length[ks]]]
model = a E^(b (x - c))/(E^(b (x - c)) + 1) + d
ff = FindFit[lst, model, a, b, c, d, x]
Plot[model /. ff, x, 0, 12, PlotRange -> 0, 12, 3, 6.5, 
 GridLines -> Automatic]

I have three sets of data aa1,aa2,aa3, I am trying to fit an equation for this data, data looks like a sigmoid function. So I have used a fit model which resembles the sigmoid function. Later I used the FindFit function to extract the unknown coefficients. when I plotted the fitted model I am getting a straight line. What mistake I am doing. same thing is happening for aa2 and aa3.

fitting

share|improve this question

asked 7 hours ago

vijay

1357

ks = 0.01, 1, 2, 4, 6, 8, 10, 25, 50, 100, 200, 300, 400, 500, 600, 
 800, 1*^3, 2*^3, 4*^3, 5*^3, 10*^3, 15*^3, 20*^3, 30*^3, 40*^3, 
 70*^3, 1*^5, 1*^6, 1*^8, 1*^12;
aa1 = 3.14172, 3.15756, 3.17331, 3.2041, 3.23399, 3.26304, 3.29131, 
 3.48223, 3.74135, 4.13211, 4.66617, 5.04019, 5.3278, 5.56008, 
 5.75347, 6.05965, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 6.28314, 
 6.28314, 6.28314;
aa2 = 9.42478, 9.42537, 9.42596, 9.42716, 9.42836, 9.42955, 9.43075, 
 9.43974, 9.45479, 9.48511, 9.54657, 9.60893, 9.67202, 9.73563, 
 9.79957, 9.92774, 10.0553, 10.6536, 11.5696, 11.9059, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663;
aa3 = 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 
 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.5663, 12.9037, 
 13.3636, 13.6161, 13.8784, 14.0112, 14.1813, 14.2487, 14.388, 
 14.4031, 14.4032;
p1 = ListLogLinearPlot[Table[ks[[i]], aa1[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p2 = ListLogLinearPlot[Table[ks[[i]], aa2[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
p3 = ListLogLinearPlot[Table[ks[[i]], aa3[[i]], i, Length[ks]], 
 Joined -> True, PlotRange -> All];
Show[p1, p2, p3, PlotRange -> All]
lst = N[Table[Log10[ks[[i]]], aa1, i, Length[ks]]]
model = a E^(b (x - c))/(E^(b (x - c)) + 1) + d
ff = FindFit[lst, model, a, b, c, d, x]
Plot[model /. ff, x, 0, 12, PlotRange -> 0, 12, 3, 6.5, 
 GridLines -> Automatic]

I have three sets of data aa1,aa2,aa3, I am trying to fit an equation for this data, data looks like a sigmoid function. So I have used a fit model which resembles the sigmoid function. Later I used the FindFit function to extract the unknown coefficients. when I plotted the fitted model I am getting a straight line. What mistake I am doing. same thing is happening for aa2 and aa3.

fitting

fitting

share|improve this question

asked 7 hours ago

vijay

1357

share|improve this question

asked 7 hours ago

vijay

1357

share|improve this question

share|improve this question

asked 7 hours ago

vijay

1357

asked 7 hours ago

vijay

1357

asked 7 hours ago

vijay

1357

1357

add a comment | 

add a comment | 

1 Answer
1

active

oldest

votes

up vote
4
down vote



accepted

In your definition of lst, I believe you forgot to add the Part specification on aa1.

lst = N[Table[Log10[ks[[i]]], aa1[[i]], i, Length[ks]]]

or

lst = Thread@Log10[ks], aa1 // N

Which then yields the final plot

share|improve this answer

edited 6 hours ago

answered 6 hours ago

That Gravity Guy

1,839514

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
  – vijay
  6 hours ago
  

  
  
  
  

add a comment | 

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
4
down vote



accepted

In your definition of lst, I believe you forgot to add the Part specification on aa1.

lst = N[Table[Log10[ks[[i]]], aa1[[i]], i, Length[ks]]]

or

lst = Thread@Log10[ks], aa1 // N

Which then yields the final plot

share|improve this answer

edited 6 hours ago

answered 6 hours ago

That Gravity Guy

1,839514

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
  – vijay
  6 hours ago
  

  
  
  
  

add a comment | 

up vote
4
down vote



accepted

In your definition of lst, I believe you forgot to add the Part specification on aa1.

lst = N[Table[Log10[ks[[i]]], aa1[[i]], i, Length[ks]]]

or

lst = Thread@Log10[ks], aa1 // N

Which then yields the final plot

share|improve this answer

edited 6 hours ago

answered 6 hours ago

That Gravity Guy

1,839514

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
  – vijay
  6 hours ago
  

  
  
  
  

add a comment | 

up vote
4
down vote



accepted

up vote
4
down vote



accepted

In your definition of lst, I believe you forgot to add the Part specification on aa1.

lst = N[Table[Log10[ks[[i]]], aa1[[i]], i, Length[ks]]]

or

lst = Thread@Log10[ks], aa1 // N

Which then yields the final plot

share|improve this answer

edited 6 hours ago

answered 6 hours ago

That Gravity Guy

1,839514

In your definition of lst, I believe you forgot to add the Part specification on aa1.

lst = N[Table[Log10[ks[[i]]], aa1[[i]], i, Length[ks]]]

or

lst = Thread@Log10[ks], aa1 // N

Which then yields the final plot

share|improve this answer

edited 6 hours ago

answered 6 hours ago

That Gravity Guy

1,839514

share|improve this answer

share|improve this answer

edited 6 hours ago

edited 6 hours ago

edited 6 hours ago

answered 6 hours ago

That Gravity Guy

1,839514

answered 6 hours ago

That Gravity Guy

1,839514

answered 6 hours ago

That Gravity Guy

1,839514

1,839514

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
  – vijay
  6 hours ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
  – vijay
  6 hours ago
  

  
  
  
  

Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
– vijay
6 hours ago

Extremely sorry, It's my mistake, I did not give attention to missing aa1[[i]]. Thanks for your time.
– vijay
6 hours ago

add a comment | 

 

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