The coefficients are then found from the poly command:Ħa. To find the coefficient of the coresonding polynomials, one first define the column vector of the roots: One finds than the coefficient of the polynomial, using the " poly" command:Īs example consider the function F(s) = s(s+50)(s+250)(s+1000). This is defined in Matlab by a column vector of the roots: Suppose that you have the following expression F(s) and would like to find the coefficient of the corresponding polynomial: FINDING THE POLYNOMIAL WHEN THE ROOS ARE KNOWN To find the roots of a polynomial of the formĪs an example consider the following function: Have multiplied the angle by 180/pi as shown above. One uses the abs() operator to find the magnitude of the complex number and theĪngle() operator to find the angle (in radians). Or one can also use the following command: I = inv(A)*B To solve this in MATLAB oneĬan use the matrix left division operator: This can be written in matrix form: A.I = B. To find the real and imaginary part of a complex number z, type:Īssume you have the following two linear comples equations with unknown The angle function gives the angle in radians. To find the magnitude and angle of z, use the abs() and angle To enter a complex number, type at the prompt: Working with complex numbers in MATLAB is easy. For more information type help plot in matlab. In the plot command, one can specify the color of the line as well as the symbol: 'b' stands for blue, 'g' for green, 'r' for red, 'y' for yellow, 'k' for black 'o' for circle, 'x' for x-mark, '+' for plus, etc. Comments can be included after the % symbol.Ĩ. In fact, in this example we could get away with only one plot command.ħ. The command "plot" can plot more than one function simultaneously. Of where the test willo appear in the figure.Ħ. In the command "text", the first two numbers give the X and Y coordinate The command "hold off" undoes the effect of "hold on".ĥ. The command "hold on" keeps the existing graph and adds the next The symbol * is used to multiply two numbers or a number and a function.ģ. at the end of a line defines the command but does not immediatelyĢ. Please note the following important point:ġ. % t is the time varying from 0 to 10 in steps of 0.1s Of MATLAB commands that will allow us to do this. In addition we want to label the figure, the horizontal and the verticalĪxes as well as each on of the the curves. Suppose we want to plot the folowing three functions:įurther more we want to use red for v1, green for v2 and blue for v3. MATLAB allows you to create plots of functions easily. Time Response of a system defined by a tranfer function.
Transfer function is given through it poles and zeros.Transfer function is defined as a ratio of two polynomials N/D, using the Bode command.Coefficient of a polynomial (from the roots).USING MATLAB FOR ELECTRIC CIRCUITS University of Pennsyvania Department of Electrical Engineering USING MATLAB FOR ELECTRICAL CIRCUITS
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