# matrix multiplication and sum- single formula

#### a7n9

##### Well-known Member
Hello all,

This problem would be difficult to explain in words, so please have a look at this sheet
Book1
ABCDEFGHIJKLMNOPQ
1V111.800V10-0.019Zin10.846Zout10.700W10.276
20.48V122.297V20-1.859Zin2-0.757Zout20.319W21.627W0-0.240Ypred0.452
3V131.992V30-1.948Zin3-0.991Zout30.271W3-0.078
4
5Zin1=0.48*1.800+(-0.019)Zout1=1/(1+exp(-Zin1)
6Zin2=0.48*2.297+(-1.859)Zout2=1/(1+exp(-Zin2)Ypred=Zout1*0.276+Zout2*1.327+Zout3*(-0.078)+(-0.240)
7Zin3=0.48*1.992+(-1.948)Zout3=1/(1+exp(-Zin3)
Sheet1

I'm interested in calculating the last value "Ypred". Therefore, I need a single formula which would calculate the products and sums as explained in the calculations. I want to eliminate intermediate steps.

Thanks for your help.

### Excel Facts

Using Function Arguments with nested formulas
If writing INDEX in Func. Arguments, type MATCH(. Use the mouse to click inside MATCH in the formula bar. Dialog switches to MATCH.
Perhaps:

=SUMPRODUCT(I1:I3,K1:K3)+M2

Hi

=SUM(1/(1+EXP(-(\$A\$2*C1:C3+E1:E3)))*K1:K3)+M2 array entered (ctrl, shift, enter)
or
=SUMPRODUCT(1/(1+EXP(-(\$A\$2*C1:C3+E1:E3))),K1:K3)+M2

if you want to eliminate the formulas in column I.

Tony

Thanks for your replies.

acw, both formuals work great, thanks. I was trying to accomplish the same thing but I wasn't able to put the 1/(1+exp(-x) thing properly. Man, you guys know some array formulas, which are hard to catch up.

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