Scilab FREAD_f block

This block is used to read data from input file stored in temporary directory or in ``my document" folder.  It has one control port and one output control port.This block uses configure options. 

1. Time record selection : It is either an empty matrix or an strictly positive integer $>0$.  If it is empty, there is no output event exists.  If an integer value, `i', is given, then  $i^{th}$ element of the read record is assumed to be the date of the output event, i.e. this record is treated as value of $t$-axis (time variable). 

2. Outputs record selection : It is a vector of positive integers like $[1,2,5]$. If read data is like a vector $[k_1, k_2, \ldots k_n]$ then $k_i^{th}$ elements of the read records, i.e. the vector made of elements $[k_1, k_2, k_5]$ is given in output.  

3. Input file name is a file name or path file name. Its value is string of characters.  

4. Buffer size : It is similar to the number of bytes read by \textit{fread} function of C language. To improve efficiency of input read, file is only done after each Buffer size call to the block. 

Each row has data record for different entity. Hence the unique data vector for each row is $[k_1, k_2, k_3]$.  If time record selection is 1, then first column will be used at $t$ values, i.e. time event values. If this option has value 2, then second column is used at time even values. Note that, time value is always $>0$ and continuous increasing, hence block stops reading of data when either time becomes negative or time starts decreasing. So, time column should be positive, greater than zero and continuous increasing.  There are three output records. If output record selection has value $1$ then only data of first column is sent as output of this block. If the  output record selection has value $[1 2 3]$ then values in first, second and third columns will be sent as output of this block. If the time record selection is 2 and output record selection is $[2, 3]$, then time for data read shall be from $t=0$ to $t=1$ seconds. After than time starts decreasing hence reading block will stop reading of data from input data file. If the time record selection is 3 and output record selection is $[2, 3]$, then time for data read shall be from $t=0$ to $t=0$ seconds as time value is negative. There will be no output.  Similarly, if time record selection option value is empty, then there is null time, hence no output. The ForTran data edit descriptors are LOGICAL, CHARACTER, INTEGER, REAL, DOUBLE PRECISION and COMPLEX which are represented by L, A, I, D, E, F or G descriptors respectively. ForTran descriptor is written as $Iw.m$ where `I' is data type, here it is integer, `w' is total field width and it must be greater than zero, `m' is minimum number of digits produced on output and it may be zero, `d' is number of digits to the right of the decimal point and it may be zero, and `e' number of digits in the exponent part and it must be greater than zero. `BN' is blank space controller. While using this format control descriptor, all embedded and trailing blanks are treated as null and ignored. Similarly, in `BZ' black control descriptor, all embedded and trailing blanks are treated as zeros. Blank space format control descriptor applies only to input and is ignored on output. `S' format control descriptor restore the system default for printing plus `+' signs. This is normally `SS' which suppress the printing of plus `+' signs in front of numerical data for the remainder of the FORMAT description. Format control descriptor `SP' force the printing of plus `+' signs in front of numerical data for the remainder of the FORMAT description. Plus sign format control descriptor are applies only to output and is ignored on input. There are column control descriptors in the ForTrans too. These are `nX' which shifts right $n$ spaces from current position. `Tn' which shifts to column $n$ in the record. `TLn' which shifts left $n$ spaces from current position. Note that you cannot shift left past column 1. This descriptor allows you to reread records on input and overwrite records on output. `TRn' which shifts right $n$ spaces from current position. Note that `TRn' is exactly equivalent to `nX'.  The slash `/' descriptor begins a new line (record) on output and skips to the next line on input, ignoring any unread information on the current record. Two slashes `//' skips one line, three slashes `///' skips two lines, etc. The format descriptor may be repeated if it is defined as $r(Fw.d)$ or $r(Fw.d,Iw.d)$. Here, `r' is an integer greater than one which specify, how many times the format descriptor inside the parentheses will be repeated. For example, $2(Fw.d)$ is equal to $Fw.d$, $Fw.d$.