From File

Purpose

Read time stamps and signal values from a file.

Library

System

Description

While a simulation is running, the From File block reads time stamps and signal values from a file. The file format can be either a text file with comma separated values (csv) or a MATLAB data file (mat).

During the simulation, the signal values for the current simulation time are read from the file and made available as a vectorized signal at the output of the From File block.

Data layout

The required input data layout differs for these two file types.

CSV file

A CSV file must contain one or more rows. The first element in each row contains a timestamp; the remaining elements contain data for the corresponding output values. Thus, the total number of columns must be equal to the parameter Number of outputs plus \(1\). The first row may contain column headers instead of numeric values. In this case, it is silently ignored.

MAT file

A MAT file must contain one matrix with real double values. Compared to the CSV file, the matrix layout is transposed. The total number of rows must be equal to the number of outputs plus \(1\). The first element in each column contains a timestamp, and the remaining elements in each column contain data for the corresponding output values.

Parameters

Filename

The name or path of the data file to read from. Relative paths are interpreted relative to the model directory.

If you choose the option literal, the string that you enter is taken literally as the basename of the data file. So, if you enter e.g. MyFile, the file name will be MyFile.csv or MyFile.mat.

If you choose the option evaluate, the string that you enter is interpreted as a MATLAB/Octave expression that must yield a string, which in turn is taken as the basename of the data file. So, if you enter e.g. ['MyFile' num2str(index)] and the current workspace contains a variable index with a value of 2, the file name will be MyFile2.csv or MyFile2.mat.

File type

The file format the specified data file has to comply to. The block can read text files with comma separated values (csv) or MATLAB data files (mat).

Number of outputs

The number of signal values in each data record (row) of the file (which is the number of columns minus one). If this number does not correspond to the actual number of signal values provided by the file, an error message is shown.

Output before first time stamp

The method used to determine the output of the From File block for simulation times before the first time stamp in the data file. Possible values are linear extrapolation, hold first value and specify value. If the parameter is set to specify value, an additional parameter field Initial output value is shown to define the output value before the first time stamp.

Initial output value

The output value before the first signal value specified in the data file. This parameter is only visible if Output before first time stamp is set to specify value. The value can be given as a scalar or a vector. If it is a scalar, it is used for all signals, if it is a vector, its size has to match the Number of outputs parameter.

Output within time range

The method used to determine the output of the From File block for simulation times between time stamps specified in the data file. Possible values are linear interpolation and zero order hold.

Output after last time stamp

The method used to determine the output of the From File block for simulation times after the last time stamp in the data file. Possible values are linear extrapolation, hold last value and specify value. If the parameter is set to specify value, an additional parameter field Final output value is shown to define the output value after the last time stamp.

Final output value

The output value after the last signal value specified in the data file. This parameter is only visible if Output after first time stamp is set to specify value. The value can be given as a scalar or a vector. If it is a scalar, it is used for all signals, if it is a vector, its size has to match the Number of outputs parameter.

Locate discontinuities

Possible values are on and off. If this parameter is set to on, the solver will ensure a time step at each time stamp specified in the data file. This setting requires a variable step solver.