### Using R to generate a random sampling table

The open source R programing language is a free software environment for statistical computing and graphics, and is easy to master. The official website is https://www.r-project.org/ . It can run on a wide variety of UNIX platforms, Windows and MacOS.

On September 24, 2016, this blog site published an article on how to use R to generate random numbers (https://consultglp.com/2016/09/24/how-to-use-r-to-generate-random-numbers/) . In light of the newly revised ISO/IEC 17025 accreditation standards embracing sampling as another important criterion for technical competence assessment, the random number function of R becomes very handy for cargo surveyors and samplers to prepare their sampling plan on cargo shipment.

We can use the random number function of R to create a random number table to suit the needs in randomly selecting samples for laboratory quality analysis.

For example, there is a shipment of 1000 bags of coffee beans in a warehouse to be surveyed prior to be dispatched to port. The buyer requires a 5% sampling for laboratory quality testing. That means some 50 bags have to be random selected before composite a portion of each bag into a suitable sized test sample through a quartering sub-sampling process.

The sampling plan, therefore, can be the following process:

1. Label each bag with a sequential number

2. Create 50 numbers in a random number table with the R command language:

> RandSampling=sample(500,50)

> dim(RandSampling)=c(10,5)

> RandSampling

[,1] [,2] [,3] [,4] [,5]

[1,] 154 424 84 486 82

[2,] 78 214 275 498 388

[3,] 93 104 478 148 258

[4,] 229 283 96 479 489

[5,] 487 211 216 59 263

[6,] 94 450 47 201 105

[7,] 330 121 130 276 56

[8,] 11 415 303 240 407

[9,] 427 60 71 142 409

[10,] 101 238 228 441 355

>

3. Sample a portion (say, 500g) of the coffee beans from the bags with these selected numbers into a large sampling bag.

4. Conduct a sample quartering process on site to reduce the test sample size to about 2.5 kg before sending to the laboratory for analysis.

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