How read values from lookup table

Hello,

I have a basic question regarding the reading of value from a table.

for example:

I have an equation , E_OC = E_P - E_N------- (i)

and i have also values of E_OC against Xc in a table, dont know any direct relation between them.

My requirements is when eqution 1 excutes ,it gives me a value of E_OC , and program should work like this ,it will give me Xc value by looking at nearmost E_OC already saved in a table.

The calcuted E_OC may be differ slighty from already saved values of E_OC against Xc.

please help me ,how I should compute this.

[Walter Roberson]

interp1 with 'nearest' interpolation.

[KIRAN noor]

it gives "NAN" for some values , I want a nearest value if exactly not lie in the table ,but not empty.

[Walter Roberson]

interp1(1:3, [1, 4, 9], 0:5, 'nearest', 'extrap')

ans = 1×6

1 1 4 9 9 9

[KIRAN noor]

Thank you Roberson,

But logically thats not correct, as whatever the range I will giveother than 1:3, it will be answe me 9.

as

>> interp1(1:3, [1, 4, 9], 0:10, 'nearest', 'extrap')

ans =

1 1 4 9 9 9 9 9 9 9 9

[Walter Roberson]

You asked

"program should work like this ,it will give me Xc value by looking at nearmost E_OC already saved in a table"

and that is what it is doing. Notice the 0 input is not extrapolating to 9, it is extrapolating to the nearest to the first parameter, 1:3 and getting 1 and looking up [1, 4, 9](1 ) to get the result.

If you want to search for the nearest to the [1 4 9] then make that the first parameter. Sometimes you want to use something like

interp1([1 4 9], [1 4 9], 0:10, 'nearest', 'extrap')

ans = 1×11

1 1 1 4 4 4 4 9 9 9 9