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About Arrays

SC2 syntax allows you to handle arrays. An array is a collection of values. For example, if you have 100 pieces of data, you can use an array to handle them all together in one variable. This is useful when you want to process a large amount of data at once.

 

 

Array variables

Declaring an array variable

 

Array variables are declared as follows:

 

Example: 100 arrays

var a[100]; // Declare an array of 100 elements.

a[0] = 123; // Assign 123 as the first element.
a[1] = 234; // Assign 234 as the second first element.
…
a[99] = 345; // Assign 345 as the 100th element.
var b = a[0] + a[1] … + a[99]; // Sum all elements of array a and assign to b.
var d = ::Math.Sum(a); // Sum all elements of array a and assign to d (Example using the Sum function)

 

 

 

 

 

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Mixing Value Types

 

Arrays can contain mixed value types, they do not have to be uniform within the array.

 

a[0] = 123;
a[1] = "hello";
a[2] = T;

 

Multidimensional array variables

 

The array variable "var a[100];" explained above is called a one-dimensional array to be precise. The SC2 syntax can also handle multidimensional arrays, and there is no limit to the number of dimensions of an array.

 

 

Declaring multidimensional array variables

 

A multidimensional array is declared as follows:

 

Example 1) Example of a two-dimensional array (10 x 100 items)

var a[10,100]; 
a[0, 0] = 1; // Assign 1 to [0, 0]
a[0, 1] = 2; // Assign 2 to [0, 1]
…
a[9, 99] = 999; // Assign 999 to [9, 99]
var b = ::Math.Ave(a); // Calculates the average of the elements in the second dimension (returns 10 1-dimensional arrays)

 

 

 

 

 

Example 2) Example of a 3-dimensional array (10 x 100 x 100 elements)

var a[10, 100, 100]; 
a[0, 0, 0] = 1; // assign 1 to [0, 0, 0]
a[0, 0, 1] = 2; // assign 2 to [0, 0, 1]
…
a[9, 99, 99] = 99999; // assign 99999 to [9, 99, 99]
var b = ::Math.Ave(a); // find the average of the third dimension elements of a (returns a 10x100 2D array)
var d = ::Math.Ave(b); // Calculates the average of the second-dimension elements of b (returns 10 one-dimensional arrays) 
var e = ::Math.Ave(d); // Calculates the average of the first-dimension elements of d (returns 1 value)

 

 

Create an array with the keyword "c"

Using the keyword "c" we can easily create arrays.

 

The format of this keyword is:

 

 

example)

var a = c(1,2,3,4); // Equivalent to "var a[4]". Each element is assigned "1,2,3,4".
var a = c(1 + 2, 3 + 4, 4 + 5); // Can contain calculations
var a = c(::GetVal("TAG1"), ::GetVal("TAG2")); // Can contain methods
var a = c(T, 123, "Hello", #2005/1/1 0:0:0#); // Can contain values of different data types

 

 

You can also combine arrays to create multidimensional arrays.

 

example)

var a = c(c(1,2), c(3,4), c(4,5)); // Same as "var a[3,2]". a[0,0] is 1, a[0,1] is 2, a[2,1] is 5. 
var a = c(c(c(1,2), c(3,4)), c(c(5,6), c(7,8))) // Same as "var a[2, 2, 2]". 

 

 

 

Array indexing

 

Declaring an array variable

 

To get an element of an array, specify the array index in [ ].

An index is a number ranging from 0 to (number of elements - 1).

 

 

 

There are the following ways to specify the index:

 

1)Specifying a number i as the index will extract the i-th element.

2)Specifying c(i, j, k, l, m….) as the index will extract the i, j, k, l, m… elements. i,j,k,l,m… do not have to be specified in ascending order. Also, duplicate values can be specified. Example: c(3,4,4,4,2,1,0)

3)If you specify an index that is a Boolean array equal to the number of elements, only the elements that are T will be extracted.

4)If you specify an index i : j, it will take the consecutive elements from i to j.

5)If no index is specified, all elements are retrieved.

 

 

Considering the method of specifying each array index based on "var a = c(1,2,3,4,5,6,7,8,9,10)",

 

1)a[ 5 ] returns the sixth element from the beginning, which is 6.

2)a[ c(2, 5, 3) ] returns the 3rd, 6th, and 4th elements from the beginning, i.e. c(3,6,4).

3)a[ c(T, T, F, F, F, T, F, F, F, T) ] extracts only the elements that are T, i.e. returns c(1,2,6,10).

4)a[ 2 : 5 ] returns the 3rd through 6th consecutive elements from the beginning, i.e. c(3,4,5,6).

5)a[] returns all elements of the array, i.e. c(1,2,3,4,5,6,7,8,9,10) is returned as is.

 

 

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Example of indexing a one-dimensional array

 

As an application of array indexing, you can extract only the elements from an array that satisfy a specified condition.

 

 

example)

var a = c(1,2,3,4,5,6,7,8,9,10)
var b = a[a > 6];

 

When the above example is executed, b will be assigned elements greater than or equal to 6, that is, c(7,8,9,10).

because a > 6 returns c(F,F,F,F,F,F,F,T,T,T,T) and as a[c(F,F,F,F,F,F,T,T,T,T,T)] returns c(7,8,9,10).

 

 

example)

var a = c("Tank abnormal", "Tank normal", "Tank open", "Pump abnormal", "Pump normal", "Pump open")
var b = a[::IsLike(a, "%abnormal%")];

 

When the above example is executed, the element containing the character "abnormality", that is, c("Tank abnormality", "Pump abnormality") will be substituted.

Because ::IsLike(a, "%Abnormal%") returns c(T,F,F,T,F,F) and as a result a[c(T,F,F,T,F,F)] returns c("Tank abnormal", "Pump abnormal").

 

 

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Indexing into multidimensional arrays

 

To get the value of an array element, specify the index of each dimension of the array in brackets [ ].

 

 

 

The method of specifying indexes is the same as for one-dimensional arrays.

 

Based on "var a = c(c(1,2), c(3,4), c(4,5))"

 

1)a[2, 0] returns the third element from the first dimension and the first element from the second dimension, which is 4.

2)a[2, ] returns the third element from the top of the first dimension, and since the second dimension is omitted, it returns all elements, that is, c(4,5).

3)a[ , 1] returns all elements in the first dimension because it is omitted, and the second element from the top in the second dimension, that is, c(2,4,5).

4)a[ c(T, F, T), ] returns the elements in the first dimension that are T, and since the second dimension is omitted, it returns all elements, that is, c(c(1,2), c(4,5)).

5)a[ 1 : 2, ] returns the second to third consecutive elements from the beginning of the first dimension, and since the second dimension is omitted, it returns all elements, that is, c(c(3,4), c(4,5)).

 

 

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Applications of indexing into multidimensional arrays

 

As an application of indexing multidimensional arrays, it is possible to extract elements by comparison as shown below.

 

example)

var a = c(c("Japan", "England", "France" , "China", "Singapore"), c("Asia", "Europ", "Europ", "Asia", "Asia"));
var b = a[0, a[1, ] == "Asia"];

 

When the above example is executed, only the country "Asia" will be extracted and c("Japan", "China", "Singapore") will be assigned to b. This is because a[1, ] == "Asia" returns c(T,F,F,T,T), and a[0, c(T,F,F,T,T)] returns c("Japan", "China", "Singapore").

 

 

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Think of a two-dimensional array as a table

 

Here, we will consider the application of indexes by comparing a two-dimensional array to a database table.

 

 

For example, if a table with 3 rows and 4 columns like the one above is expressed using the keyword "c", it will look like this:

a = c( c(1,2,3),
	c(“Test1”,”Test2”,”Test3”),
	c(T,F,T),
	c(#2005/1/1 12:30:00#, #2005/1/1 14:25:00#, #2005/1/1 15:15:00#) );

 

 

In this example, the following indexes are possible:

 

1.a[0, ] is the 0th column, that is, c(1,2,3).

 

2.::Math.Ave(a[0, ]) is the average value of the 0th column, which is 2.

 

3.a[c(1,2), ] is the first and second columns, and the result is as follows.

c(c(“Test1”,”Test2”,”Test3”),
c(T,F,T) );

 

 

4.a[c(1,1) , ] are all the first columns, and the results are as follows.

c(c(T,F,T),
  c(T,F,T) );

 

 

5.a[ , a[3, ] > #2005/1/1 14:00:00#] retrieves records from "2005/1/1 14:00:00" onwards.

c(c(2,3),
c(”Test2”,”Test3”),
c(F,T),
c(”#2005/1/1 14:25:00#”,”#2005/1/1 15:15:00#”) );

 

 

6.::Math.Ave(a[0 , a[3, ] > #2005/1/1 14:00:00#]) calculates the average value of column 0 of the records after "2005/1/1 14:00:00". In other words, the average value of c(2,3), the result is 2.5.