cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
JMP is taking Discovery online, April 16 and 18. Register today and join us for interactive sessions featuring popular presentation topics, networking, and discussions with the experts.
Choose Language Hide Translation Bar
natalie_
Level V

Calculating Derivatives/Slopes in JMP

Hello again,

I have to columns of data, let's call them x and y.  I want to calculate the center derivative of y with respect to x (dy/dx).  If I am using the center derivative, that means I will be "missing" a point at the beginning and end of the dy/dx column.

For example, in row two of dy/dx, I want it to equal dy/dx = y3-y1/x3-x1 and on row three of dy/dx, I want it to equal dy/dx = y4-y2/x4-x2.  I am having a hard time not using jmp like I would with excel, so I am not even sure if is possible to do this in the formula editor.

Thanks!

1 ACCEPTED SOLUTION

Accepted Solutions
pmroz
Super User

Re: Calculating Derivatives/Slopes in JMP

This code should give you some ideas.  The column formula makes use of the LAG function:

dt = open("$sample_data\Big Class.jmp");

// Create formula column

// Height = X

// Weight = Y

// dy/dx = (y+1) - (y-1)/(x+1) - (x-1)

// y+1: lag(:weight, -1)

// y-1: lag(:weight, 1)

// x+1: lag(:height, -1)

// x-1: lag(:height, 1)

dt << New Column( "dy/dx",

            Numeric,

            Continuous,

            Format( "Best", 12 ),

            Formula( lag(:weight, -1) - lag(:weight, 1) / lag(:height, -1) - lag(:height, 1))

      );

View solution in original post

3 REPLIES 3
DaveLee
Level IV

Re: Calculating Derivatives/Slopes in JMP

natalie_,

The Formula Editor has a derivative option.  You can access it by clicking the red triangle at the top of the Editor dialog. 

10730_pastedImage_0.png

Hope this helps.


Dave

pmroz
Super User

Re: Calculating Derivatives/Slopes in JMP

This code should give you some ideas.  The column formula makes use of the LAG function:

dt = open("$sample_data\Big Class.jmp");

// Create formula column

// Height = X

// Weight = Y

// dy/dx = (y+1) - (y-1)/(x+1) - (x-1)

// y+1: lag(:weight, -1)

// y-1: lag(:weight, 1)

// x+1: lag(:height, -1)

// x-1: lag(:height, 1)

dt << New Column( "dy/dx",

            Numeric,

            Continuous,

            Format( "Best", 12 ),

            Formula( lag(:weight, -1) - lag(:weight, 1) / lag(:height, -1) - lag(:height, 1))

      );

natalie_
Level V

Re: Calculating Derivatives/Slopes in JMP

Thank you, it worked well.

I used it in a script, but I had to add As Column. 

col <<Set Formula( (lag(As Column("Y"), -1) - lag(As Column("Y"),1))/(lag(As Column("X"),-1)-lag(As Column("X"),1)));