Error while using farver::encode_colour

[ericmelse]

Dear Thomas,

With great interest I am exploring your fine package farver but I have issues while using farver::encode_colour
My objective is to calculate color codes between color spaces. Here I get a range of colours in CIELAB space using:

lab_a_L50 <- farver::encode_colour(
  cbind(l=50,
        a=c(-100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100),
        b=0), from="lab")
lab_a_L50
# [1] "#009775" "#009575" "#009375" "#009175" "#008E75" "#008B76" "#008876" "#2A8476" "#4C8076" "#647C77" "#777777" "#887177" "#986B78" "#A66378" "#B45A78" "#C24F79"
# [17] "#CF4179" "#DC2C7A" "#E8007A" "#F5007B" "#FF007B"

That works just fine and next I create a figure with the result data, like:

With the above I want to show (graded) colors along the CIELAB a-axis with the b-axis value of each color set to 0 (neutral point) at the lightness level set to 50.

But, now I want to do the same for the CIELAB b-axis using this command:

lab_b_L50 <- farver::encode_colour(
  cbind(l=50,
        a=0,
        b=c(-100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100), from="lab")
lab_b_L50

As such the command code runs without any complaint, but using lab_b_L50 after that results in the error message:

Error: unexpected symbol in:
"        b=c(-100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100), from="lab")
lab_b_L50"

I also tried:

lab_b_L50 <- farver::encode_colour(
  cbind(l=50,
       a=c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
       b=c(-100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100), from="lab")
lab_b_L50

which produces the same error message.
Note that this command code (for the a-axis):

lab_a_L50 <- farver::encode_colour(
  cbind(l=50,
        a=c(-100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100),
        b=c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0), from="lab")
lab_a_L50

also produces the same error message.

So, maybe I am confused about how to set values for the a and b axis (dimension) in CIELAB but so far I found only one example in the documention that produces the expected result (which I used succesfully for the first example above).

Time permitting, I really apreciate your helping hand how to properly set such parameters for CIELAB (and OKLAB).

Best,
Eric

[ericmelse]

Dear Thomas,
While exercising with your farver package , I also used the r-wizard of the chatgpt website and that resulted in the correct code:

lab_b_L50 <- farver::encode_colour(
  cbind(l=50,
        a=0,
        b=c(-100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100)), from="lab")
lab_b_L50

That works just fine and next I create a figure with the result data, like:

So, my little tricky error was that I did not use a second closing bracket that is required )), from="lab")

For those interested in calculating the CIELAB AB plane at a given L-value, this is code how to produce that:

# Create a plane of colors for the CIELAB color space using the farver package
# Define the range and step size for a and b
a_range <- seq(-100, 100, by = 10)
b_range <- seq(-100, 100, by = 10)

# Create a grid of a and b values
lab_grid <- expand.grid(a = a_range, b = b_range)

# Define the constant lightness (L) value
lab_L <- 50

# Create the colors using the farver package
lab_AxB_L50_10 <- farver::encode_colour(
  cbind(
    l = lab_L,
    a = lab_grid$a,
    b = lab_grid$b
  ), from = "lab"
)

Which results in: