บทที่ 3- ฟังก์ชันไซแลบที่มีประโยขน์ในการวิเคราะห์

Chapter 3 – Useful Scilab functions In analysis 32
In probability and statistics 32
To display and plot 33
Utilities 33

chapter 3 – Useful Scilab functions Analysis • sqrt(x) returns the square root of � with � real positive or zero, and the complex root of real positive part otherwise. • log(x) returns the natural logarithm of x with x real or complex number. • exp(x) returns the exponential of � with � real or complex number. • abs(x) returns the absolute value of � real (or the module if � is complex). • int(x) returns the truncation of � real (the integer before the decimal). • floor(x) returns the integer part of � real (the integer � for which � ≤ � < � + 1). • ceil(x) for � real returns the integer � for which � − 1 < � ≤ �. Probability and statistics • factorial(n) returns the factorial of n with n positive or zero integer. • grand(1,p,"uin",m,n) returns a vector of p random integer sequences taken between m and n with p positive integer, m and n integers and � ≤ �. • grand(1,p,"unf",a,b) returns a vector of p random real sequences taken between a and b with p positive integer, a and b real and � ≤ �. • sum(n) returns the sum of the values of vector � (used to calculate a total). • cumsum(n) returns the vector of increasing cumulative values of vector � (used to calculate the increasing cumulative numbers). • length(v) returns the number of coordinates of vector �. • gsort(v) returns the vector of numbers or strings � sorted in descending order. • gsort(v,"g","i") returns the vector of numbers or strings � sorted in ascending order. • mean(v) returns the average of the vector of numbers �. • stdev(v) returns the standard deviation of numbers � vector. • bar(v,n,couleur) draws the bar graph with � as X-coordinate, � as Y-coordinate, � and � being same size line vectors. By default, bar(n) draws the bar graph of � in blue with 1,2,3… as X-coordinates. • bar(v,[n1’,n2’]) draws a double bar graph with � as X-coordinate, n1 as Ycoordinate in blue and n2 as Y-coordinate in green, with �, n1 and n2 being same size line vectors. • rand(n,p) with � and � positive integers, returns a matrix �×� of numbers randomly taken between 0 and 1. • rand() returns a real number randomly taken between 0 and 1. • floor(x) returns the integer part of � real number. In particular, if � is real between 0 and 1, floor(rand()+p) will be 1 with � probability and 0 with 1 − � probability. Scilab for very beginners - 33/33 Display and plot • clf means “ clear figure “ and clears the current figure on the graphics window. • plot allows to draw curves and scatter plots in 2 dimensions. • linspace(a,b,n), with � and � real and � integer, defines a vector of � values regularly spaced between � and �. • scf allows to open or to select other graphics windows than the current one. • surf allows 3-D surface plots. • bar(X,Y) in which X and Y are vectors, draws the bar graph of the series of values for X which has for numbers the values of Y. • plot(X,Y,"*") draws the scatter plot of coordinates (X(i),Y(i)) as stars. The color can be specified. • plot(Y,"+") draws the scatter plot of coordinates (i,Y(i)) as cross. • disp("Sentence") displays what is written in double quotes. • disp(A) in which A is a matrix of numbers, displays the table of the values of A. • disp("Sentence"+string(x)) displays the sentence and the value of number �. • xclick returns the coordinates of the point clicked in a graphics window. Utilities • unique(v) returns the vector � with a unique occurrence of its repeated components. • sum(v) returns the sum of all the elements of the vector or the matrix �. • prod(v) returns the product of all the elements of the vector or the matrix �. • find() returns the indices of the elements of vector � satisfying the test. • disp(x,y,…) displays the values of its arguments in the console. • string(x) converts number � to a string. • format(n) in which � is an integer greater than or equal to 2, sets the display to � characters, including the sign and the decimal dot. • zeros(n,p) defines a �×� matrix that only contains zeros. • feval(x,y,f) in which � and � are respectively vectors of size � and �, defines the matrix �×� whose element (�,�) is �(� � , � � ). • help function opens the help browser on the right function page. • tic starts a clock. • toc stops the clock.