R Under development (unstable) (2025-07-25 r88451 ucrt) -- "Unsuffered Consequences"
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> library(chapensk)
Loading required package: Bessel
> 
> # graphics parameters
> width <- 10
> height <- 5
> mar <- c(5.1, 4.6, 0.2, 0.6)
> mai <- c(1.02, 0.82, 0.04, 0.04)
> family <- "Helvetica"
> pointsize <- 12
> lwd <- 1
> 
> c2h6 <- Gas("ethane")
> 
> if (interactive()) {
+   if (exists("outputDevice")) {
+     if (outputDevice == "pdf") pdf(file = "man/figures/ethane.pdf", width = width, height = height, family = family, pointsize = pointsize)
+     if (outputDevice == "svg") svg(file = "man/figures/ethane.svg", width = width, height = height, family = family, pointsize = pointsize)
+   }
+   split.screen(figs = c(1, 2))
+ }
> 
> ethane_viscosity <- subset(ethane_data, (property == "viscosity") & (T >= 90) & (T <= 675), select = c(T, value))
> sigma0 <- c2h6$sigma
> epsk0 <- c2h6$epsk
> c2h6$zeta <- 0
> print("Literature data")
[1] "Literature data"
> print(c2h6$sigma)
[1] 4.443
> print(c2h6$epsk)
[1] 215.7
> ethane_viscosity$value <- 1E-6 * ethane_viscosity$value
> ethane_B <- subset(ethane_data, (property == "BQFH") & (T >= 220) & (T <= 623))
> ethane_B$value <- 1E-6 * ethane_B$value
> fit <- c2h6$fit_B_viscosity_data(ethane_B, ethane_viscosity, log = FALSE)
> sigma1 <- c2h6$sigma
> epsk1 <- c2h6$epsk
> zeta1 <- c2h6$zeta
> print("Fit of B and viscosity data")
[1] "Fit of B and viscosity data"
> print(c2h6$sigma)
[1] 4.358396
> print(c2h6$epsk)
[1] 244.8239
> print(c2h6$zeta)
[1] 0
> stopifnot(round(c2h6$sigma, 2) == 4.36)
> stopifnot(round(c2h6$epsk, 1) == 244.8)
> c2h6$sigma <- sigma0
> c2h6$epsk <- epsk0
> c2h6$zeta <- 0
> if (interactive()) {
+   screen(1)
+ }
> par(mai = mai, mar = mar)
> c2h6$fit_viscosity_data(ethane_viscosity)
3.217631e-13 (7.05e-01): par = (4.443 215.7)
2.078813e-13 (1.23e-01): par = (4.387213 232.5813)
2.045675e-13 (1.14e-02): par = (4.379045 235.3511)
2.045379e-13 (1.20e-03): par = (4.378 235.6692)
2.045376e-13 (1.27e-04): par = (4.377886 235.7031)
2.045376e-13 (1.34e-05): par = (4.377874 235.7067)
2.045376e-13 (1.47e-06): par = (4.377872 235.707)

Formula: value ~ .self$viscosity(T, sigma, epsk, zeta = 0, third_order_correction = TRUE)

Parameters:
       Estimate Std. Error t value Pr(>|t|)    
sigma   4.37787    0.02068  211.71   <2e-16 ***
epsk  235.70704    6.01015   39.22   <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 9.642e-08 on 22 degrees of freedom

Number of iterations to convergence: 6 
Achieved convergence tolerance: 1.474e-06

> lines(ethane_viscosity$T, 1E6 * c2h6$viscosity(ethane_viscosity$T, sigma = sigma1, epsk = epsk1, zeta = zeta1), col = "red", lty = 2)
> if (interactive()) {
+   legend("top", bty = "n", legend = "(a)")
+   screen(2)
+ }
> print("Fit of viscosity data")
[1] "Fit of viscosity data"
> print(c2h6$sigma)
[1] 4.377872
> print(c2h6$epsk)
[1] 235.707
> stopifnot(round(c2h6$sigma, 2) == 4.38)
> stopifnot(round(c2h6$epsk, 1) == 235.7)
> par(mai = mai, mar = mar)
> c2h6$zeta <- 0
> c2h6$fit_B_data(ethane_B)
3.298456e-09 (2.96e+00): par = (4.377872 235.707)
1.793282e-09 (2.19e+00): par = (4.70964 211.6114)
3.304397e-10 (2.73e-01): par = (4.961272 200.5874)
3.075578e-10 (2.91e-03): par = (4.950029 201.9349)
3.075552e-10 (2.71e-05): par = (4.949684 201.9616)
3.075552e-10 (3.99e-07): par = (4.949678 201.962)

Formula: value ~ .self$B(T, sigma, epsk, zeta = 0)

Parameters:
       Estimate Std. Error t value Pr(>|t|)    
sigma   4.94968    0.05755   86.00   <2e-16 ***
epsk  201.96198    3.45749   58.41   <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 4.528e-06 on 15 degrees of freedom

Number of iterations to convergence: 5 
Achieved convergence tolerance: 3.995e-07

> lines(ethane_B$T, 1E6 * c2h6$B(ethane_B$T, sigma = sigma1, epsk = epsk1), col = "red", lty = 2)
> if (interactive()) {
+   legend("top", bty = "n", legend = "(b)")
+   close.screen()
+   dev.off()
+ }
> print("Fit of B data")
[1] "Fit of B data"
> print(c2h6$sigma)
[1] 4.949678
> print(c2h6$epsk)
[1] 201.962
> stopifnot(round(c2h6$sigma, 2) == 4.95)
> stopifnot(round(c2h6$epsk, 1) == 202.0)
> 
> proc.time()
   user  system elapsed 
    2.1     0.1     2.2