Thread: Estimating partial derivatives using a table

1. Estimating partial derivatives using a table

So, here are the values given on the table (I tried to upload an image, but I couldn't get it any bigger):

K = 25, L = 700 : 2663.4; K = 30, L = 700 : 2917.9; K = 35, L = 700 : 3151.7
K = 25, L = 720 : 2688.8; K = 30, L = 720 : 2945.5; K = 35, L = 720 : 3181.5
K = 25, L = 740 : 2713.5; K = 30, L = 740 : 2972.5; K = 35, L = 740 : 3210.7
K = 25, L = 760 : 2737.5; K = 30, L = 760 : 2999.0; K = 35, L = 760 : 3239.3

(On the table, K is on the left side of the table and L is along the top; i.e., K is y and L is x).
The problem is to define the partial derivatives dP/dK and dP/dL at the point K = 30, L = 740.

My work:

For dP/dK, I did (2972.5-2713.5)/5 + (3210.7-2972.5)/5 = 99.44
And for dP/dL, I did (2972.5-2945.4)/20 + (2999.0-2972.5)/20 = -0.325

Did I do this right? Any input would be appreciated.

2. Originally Posted by Rumor
So, here are the values given on the table (I tried to upload an image, but I couldn't get it any bigger):

K = 25, L = 700 : 2663.4; K = 30, L = 700 : 2917.9; K = 35, L = 700 : 3151.7
K = 25, L = 720 : 2688.8; K = 30, L = 720 : 2945.5; K = 35, L = 720 : 3181.5
K = 25, L = 740 : 2713.5; K = 30, L = 740 : 2972.5; K = 35, L = 740 : 3210.7
K = 25, L = 760 : 2737.5; K = 30, L = 760 : 2999.0; K = 35, L = 760 : 3239.3

(On the table, K is on the left side of the table and L is along the top; i.e., K is y and L is x).
The problem is to define the partial derivatives dP/dK and dP/dL at the point K = 30, L = 740.

My work:

For dP/dK, I did (2972.5-2713.5)/5 + (3210.7-2972.5)/5 = 99.44
And for dP/dL, I did (2972.5-2945.4)/20 + (2999.0-2972.5)/20 = -0.325

Did I do this right? Any input would be appreciated.
That looks an acceptable method, though rather more arithmetic than you need since the central term cancells in both..

CB

,

estimate partial derivative

Click on a term to search for related topics.