Outside compensation curve

[jerryhenke]

Hello.

You can try this:

Code:

function linear_by_table(input,curve,offset) local FDY = offset or 0     fk1= (curve["y"][1] - curve["y"][2]) / (curve["x"][1] - curve["x"][2])     fk2= (curve["y"][2] - curve["y"][3]) / (curve["x"][2] - curve["x"][3])     fk3= (curve["y"][3] - curve["y"][4]) / (curve["x"][3] - curve["x"][4])     if input < curve["x"][1] then         out = curve["y"][1] + FDY;     elseif input >= curve["x"][1] and input < curve["x"][2] then             out = fk1 * (input - curve["x"][1]) + curve["y"][1] + FDY     elseif input >= curve["x"][2] and input < curve["x"][3] then         out = fk2 * (input - curve["x"][2]) + curve["y"][2] + FDY     elseif input >= curve["x"][3] and input < curve["x"][4] then             out = fk3 * (input - curve["x"][3]) + curve["y"][3] + FDY     else         out = curve["y"][4] + FDY     end  return out end curve = {} curve["x"] = {-20,-10,0,20} curve["y"] = {80,70,65,18} --offset=2 --log(linear_by_table(20,curve,offset)) log(linear_by_table(-15,curve))

Wow. Thanks! Used this today and made some small changes.

My code looks like this and runs nicely.
 

Code:

function linear_by_table(input, curve, offset)     local FDY = offset or 0     local n = #curve["x"] -- Number of points     if n ~= #curve["y"] then         error("x and y lists must have the same number of values")     end     local out     if input < curve["x"][1] then         out = curve["y"][1] + FDY     elseif input >= curve["x"][n] then         out = curve["y"][n] + FDY     else         for i = 1, n - 1 do             if input >= curve["x"][i] and input < curve["x"][i + 1] then                 local fk = (curve["y"][i + 1] - curve["y"][i]) / (curve["x"][i + 1] - curve["x"][i])                 out = fk * (input - curve["x"][i]) + curve["y"][i] + FDY                 break             end         end     end     return out end -- Define the curve for interpolation local curve = {x = {-20, -10, 0, 10, 20}, y = {42, 34, 32, 25, 15}} -- Adjust offset to shift the entire curve local offset = 0 -- Get outdoor temperature from KNX address 0/3/0 local outdoor_temp = grp.getvalue('0/3/0') -- Calculate the flow setpoint based on the outdoor temperature local flow_setpoint = linear_by_table(outdoor_temp, curve, offset) -- Write the calculated value to KNX address 5/5/0 grp.write('5/5/0', flow_setpoint) -- Log the results log('Outdoor temperature: ' .. outdoor_temp .. ', Flow setpoint: ' .. flow_setpoint)