CombiTable1Ds

Table look-up in one dimension (matrix/file) with one input and n outputs

Library

Modelica/Blocks/Tables

Description

Univariate constant, linear or cubic Hermite spline interpolation in one dimension of a table. Via parameter columns it can be defined how many columns of the table are interpolated. If, e.g., columns={2,4}, it is assumed that 2 output signals are present and that the first output interpolates via column 2 and the second output interpolates via column 4 of the table matrix.

The grid points and function values are stored in a matrix "table[i,j]", where the first column "table[:,1]" contains the grid points and the other columns contain the data to be interpolated. Example:

   table = [0,  0;
1,  1;
2,  4;
4, 16]
If, e.g., the input u = 1.0, the output y =  1.0,
e.g., the input u = 1.5, the output y =  2.5,
e.g., the input u = 2.0, the output y =  4.0,
e.g., the input u =-1.0, the output y = -1.0 (i.e., extrapolation).

• The interpolation interval is found by a binary search where the interval used in the last call is used as start interval.
• Via parameter smoothness it is defined how the data is interpolated:
  smoothness = 1: Linear interpolation
= 2: Akima interpolation: Smooth interpolation by cubic Hermite
splines such that der(y) is continuous, also if extrapolated.
= 3: Constant segments
= 4: Fritsch-Butland interpolation: Smooth interpolation by cubic
Hermite splines such that y preserves the monotonicity and
der(y) is continuous, also if extrapolated.
= 5: Steffen interpolation: Smooth interpolation by cubic Hermite
splines such that y preserves the monotonicity and der(y)
is continuous, also if extrapolated.

• Values outside of the table range, are computed by extrapolation according to the setting of parameter extrapolation:
  extrapolation = 1: Hold the first or last value of the table,
if outside of the table scope.
= 2: Extrapolate by using the derivative at the first/last table
points if outside of the table scope.
(If smoothness is LinearSegments or ConstantSegments
this means to extrapolate linearly through the first/last
two table points.).
= 3: Periodically repeat the table data (periodical function).
= 4: No extrapolation, i.e. extrapolation triggers an error

• If the table has only one row, the table value is returned, independent of the value of the input signal.
• The grid values (first column) have to be strictly increasing.

The table matrix can be defined in the following ways:

1. Explicitly supplied as parameter matrix "table", and the other parameters have the following values:
   tableName is "NoName" or has only blanks,
fileName  is "NoName" or has only blanks.

2. Read from a file "fileName" where the matrix is stored as "tableName". Both text and MATLAB MAT-file format is possible. (The text format is described below). The MAT-file format comes in four different versions: v4, v6, v7 and v7.3. The library supports at least v4, v6 and v7 whereas v7.3 is optional. It is most convenient to generate the MAT-file from FreeMat or MATLAB® by command
   save tables.mat tab1 tab2 tab3

or Scilab by command
   savematfile tables.mat tab1 tab2 tab3

when the three tables tab1, tab2, tab3 should be used from the model.
Note, a fileName can be defined as URI by using the helper function loadResource.
3. Statically stored in function "usertab" in file "usertab.c". The matrix is identified by "tableName". Parameter fileName = "NoName" or has only blanks. Row-wise storage is always to be preferred as otherwise the table is reallocated and transposed. See the Tables package documentation for more details.

When the constant "NO_FILE_SYSTEM" is defined, all file I/O related parts of the source code are removed by the C-preprocessor, such that no access to files takes place.

If tables are read from a text file, the file needs to have the following structure ("-----" is not part of the file content):

-----------------------------------------------------
#1
double tab1(5,2)   # comment line
0   0
1   1
2   4
3   9
4  16
double tab2(5,2)   # another comment line
0   0
2   2
4   8
6  18
8  32
-----------------------------------------------------


Note, that the first two characters in the file need to be "#1" (a line comment defining the version number of the file format). Afterwards, the corresponding matrix has to be declared with type (= "double" or "float"), name and actual dimensions. Finally, in successive rows of the file, the elements of the matrix have to be given. The elements have to be provided as a sequence of numbers in row-wise order (therefore a matrix row can span several lines in the file and need not start at the beginning of a line). Numbers have to be given according to C syntax (such as 2.3, -2, +2.e4). Number separators are spaces, tab (\\t), comma (,), or semicolon (;). Several matrices may be defined one after another. Line comments start with the hash symbol (#) and can appear everywhere. Text files should either be ASCII or UTF-8 encoded, where UTF-8 encoded strings are only allowed in line comments and an optional UTF-8 BOM at the start of the text file is ignored. Other characters, like trailing non comments, are not allowed in the file.

MATLAB is a registered trademark of The MathWorks, Inc.

Parameters

NameLabelDescriptionData TypeValid Values

mo_nout

nout

Number of outputs

Scalar

mo_tableOnFile

tableOnFile

= true, if table is defined on file or in function usertab

Scalar

true
false

mo_table

table

Table matrix (grid = first column; e.g., table=[0, 0; 1, 1; 2, 4])

Matrix

mo_tableName

tableName

Table name on file or in function usertab (see docu)

String

mo_fileName

fileName

File where matrix is stored

String

= true, if info message that file is loading is to be printed

Scalar

true
false

mo_columns

columns

Columns of table to be interpolated

Vector

mo_smoothness

smoothness

Smoothness of table interpolation

Structure

mo_smoothness/choice1

Table points are linearly interpolated

Number

0
1

mo_smoothness/choice2

Table points are interpolated (by Akima splines) such that the first derivative is continuous

Number

0
1

mo_smoothness/choice3

Table points are not interpolated, but the value from the previous abscissa point is returned

Number

0
1

mo_smoothness/choice4

Table points are interpolated (by Fritsch-Butland splines) such that the monotonicity is preserved and the first derivative is continuous

Number

0
1

mo_smoothness/choice5

Table points are interpolated (by Steffen splines) such that the monotonicity is preserved and the first derivative is continuous

Number

0
1

mo_extrapolation

extrapolation

Extrapolation of data outside the definition range

Structure

mo_extrapolation/choice1

Hold the first/last table point outside of the table scope

Number

0
1

mo_extrapolation/choice2

Extrapolate by using the derivative at the first/last table points outside of the table scope

Number

0
1

mo_extrapolation/choice3

Repeat the table scope periodically

Number

0
1

mo_extrapolation/choice4

Extrapolation triggers an error

Number

0
1

mo_verboseExtrapolation

verboseExtrapolation

= true, if warning messages are to be printed if table input is outside the definition range

Scalar

true
false

mo_u_min

u_min

Minimum abscissa value defined in table

Scalar

mo_u_max

u_max

Maximum abscissa value defined in table

Scalar

mo_tableID

tableID

External table object

Scalar

NameLabelDescriptionData TypeValid Values

mo_u

u

u

Structure

mo_u/fixed

fixed

Cell of scalars

true
false

mo_u/start

start

Cell of scalars

mo_y

y

y

Structure

mo_y/fixed

fixed

Cell of vectors

true
false

mo_y/start

start

Cell of vectors

Ports

NameTypeDescriptionIO TypeNumber

u

implicit

Connector of Real input signal

input

1

y

implicit

Connector of Real output signals

output

1