# TI Program

• May 10th 2008, 03:56 AM
tomjkear
TI Program

Can anyone tell me how to do the following equation on a calculator?

1 / [1 + e-(1*0.5+1*0.4-1*0.8)]

Cheers,
TK
• May 10th 2008, 04:00 AM
Moo
Quote:

Originally Posted by tomjkear

Can anyone tell me how to do the following equation on a calculator?

1 / [1 + e-(1*0.5+1*0.4-1*0.8)

Cheers,
TK

Hello,

There is no equation in there... oO
And which calculator ?
• May 10th 2008, 04:03 AM
tomjkear
Quote:

Originally Posted by Moo
Hello,

There is no equation in there... oO
And which calculator ?

That is a sigmoidal function.

I do not understand the purpose / value of e?
• May 10th 2008, 04:13 AM
Moo
Quote:

Originally Posted by tomjkear
That is a sigmoidal function.

I do not understand the purpose / value of e?

Oh, I see

e has a value approaching 2.7. Actually it's e^(...).
It's the exponential function : Exponential function - Wikipedia, the free encyclopedia

So if you want to enter the function in your calculator, it should be :

1/(1+e^(-(1*0.5+1*0.4-1*0.8)))
• May 10th 2008, 04:17 AM
tomjkear
Quote:

Originally Posted by Moo
Oh, I see

e has a value approaching 2.7. Actually it's e^(...).
It's the exponential function : Exponential function - Wikipedia, the free encyclopedia

So if you want to enter the function in your calculator, it should be :

1/(1+e^(-(1*0.5+1*0.4-1*0.8)))

Thanks.

I know the result should be 0.5250 according to the textbook I am using. But doing the above in my calculator returns 0.5 for some reason.

Another similar example that is given is:

1/(1+e^(-(1*0.9+1*1.0+1*0.1)))

This should return 0.8808 but also returns 0.5 on my calculator.

If it helps the calculator is a Sharp EL-530L.
• May 10th 2008, 04:26 AM
Moo
Quote:

Originally Posted by tomjkear
Thanks.

I know the result should be 0.5250 according to the textbook I am using. But doing the above in my calculator returns 0.5 for some reason.

Another similar example that is given is:

1/(1+e^(-(1*0.9+1*1.0+1*0.1)))

This should return 0.8808 but also returns 0.5 on my calculator.

If it helps the calculator is a Sharp EL-530L.

I don't know this calculator, so I don't know what e represents for them...

Try typing :

1/(1+2.71828183^(-(1*0.9+1*1.0+1*0.1)))

(because e ~ 2,71828183)
• May 10th 2008, 04:40 AM
tomjkear
Quote:

Originally Posted by Moo
I don't know this calculator, so I don't know what e represents for them...

Try typing :

1/(1+2.71828183^(-(1*0.9+1*1.0+1*0.1)))

(because e ~ 2,71828183)

Thanks for the help.
I have tried a diffferent calculator and it returns the correct results.
Not sure what is the matter with mine but I will get a replacement for the exam :)