Equivalent functions generate different plots

• To: mathgroup at smc.vnet.net
• Subject: [mg26112] Equivalent functions generate different plots
• From: GERMAN <gerbual at col2.telecom.com.co>
• Date: Tue, 28 Nov 2000 01:55:59 -0500 (EST)
• Organization: Universidad Nacional de Colombia
• Sender: owner-wri-mathgroup at wolfram.com

```Hi, Group:

With:

In[1]:=
data = {{0, 79.6}, {0.2, 79.2}, {0.4, 77.1}, {0.6, 73.7}, {0.8, 69.1},
{1., 63.2}};

I can to get its cuadratic regression function:

In[2]:=
Fit[data, {1, t, t^2}, t]

Out[2]=
79.68214285714285` + 0.21249999999984936` t - 16.741071428571246` t^2

Then, I can define the regression function in two different, but
equivalent ways:

First: copying and pasting the last output:

In[3]:=
f[t_] :=
79.68214285714285`+ 0.21249999999984936` t - 16.741071428571246 t^2

Second: using directly the *Fit* function in the right hand:

In[4]:=
g[t_] := Fit[data, {1, t, t^2}, t]

In this conditions:

In[5]:=
f[t] == g[t]

Out[5]=
True

However:

In[6]:=
Plot[{f[t], g[t]}, {t, 0, 2.2}]

Out[6]=

(GRAPHICS ...!!!)

genere two different plots (a straight line and a curve). The curve is
well, but the straight line not. I DON'T UNDERSTAND. Can somebody
explain to me this inconsistency?