gsw_entropy_second_derivatives: Second Derivatives of Entropy

View source: R/gsw.R

gsw_entropy_second_derivativesR Documentation

Second Derivatives of Entropy


Second Derivatives of Entropy


gsw_entropy_second_derivatives(SA, CT)



Absolute Salinity [ g/kg ]


Conservative Temperature [ degC ]


A list containing eta_SA_SA [ (J/(K*kg))/(g/kg)^2 ], the second derivative of entropy with respect to Absolute Salinity, eta_SA_CT [ (J/(K*kg))/(K*g/kg) ], the derivative of entropy with respect to Absolute Salinity and Conservative Temperature, and eta_CT_CT [ (J/(K*kg))/K^2 ], the second derivative of entropy with respect to Conservative Temperature.

Implementation Note

This R function uses a wrapper to a C function contained within the GSW-C system as updated 2021-12-28 at with git commit '98f0fd40dd9ceb0ba82c9d47ac750e935a7d0459'.

The C function uses data from the library/gsw_data_v3_0.mat file provided in the GSW-Matlab source code, version 3.06-11. Unfortunately, this version of the mat file is no longer displayed on the website. Therefore, in the interests of making GSW-R be self-contained, a copy was downloaded from on 2022-05-25, the .mat file was stored in the developer/create_data directory of, and then the dataset used in GSW-R was created based on that .mat file.

Please consult to learn more about the various TEOS-10 software systems.



SA <- c(34.7118, 34.8915, 35.0256, 34.8472, 34.7366, 34.7324)
CT <- c(28.8099, 28.4392, 22.7862, 10.2262,  6.8272,  4.3236)
r <- gsw_entropy_second_derivatives(SA, CT)
stopifnot(all.equal(r$eta_SA_SA, c(-0.007627718929669, -0.007591969960708, -0.007528186784540,
                                   -0.007455177590576, -0.007441108287466, -0.007414368396280)))
stopifnot(all.equal(r$eta_SA_CT, c(-0.001833104216751, -0.001819473824306, -0.001580843823414,
                                   -0.000930111408561, -0.000717011215195, -0.000548410546830)))
stopifnot(all.equal(r$eta_CT_CT, c(-0.043665023731109, -0.043781336189326, -0.045506114440888,
                                   -0.049708939454018, -0.050938690879443, -0.051875017843472)))

gsw documentation built on Oct. 16, 2022, 5:06 p.m.