Question

matlab中找不到step函数

如题，在command window输入step函数，给出“Undefined function 'step' for input arguments of type 'double'.”
是我的matlab没有安装完全吗？ 用的是2012b版本

Answer 1

在命令行输入help step即可。
如下所示，可以 看到函数step的用法。
>> help step
STEP Step response of dynamic systems.

STEP(SYS) plots the step response of the dynamic system SYS. For
multi-input models, independent step commands are applied to each
input channel. The time range and number of points are chosen
automatically.

STEP(SYS,TFINAL) simulates the step response from t=0 to the
final time t=TFINAL. For discrete-time models with unspecified
sampling time, TFINAL is interpreted as the number of samples.

STEP(SYS,T) uses the user-supplied time vector T for simulation.
For discrete-time models, T should be of the form Ti:Ts:Tf
where Ts is the sample time. For continuous-time models,
T should be of the form Ti:dt:Tf where dt will become the sample
time for the discrete approximation to the continuous system. The
step input is always assumed to start at t=0 (regardless of Ti).

STEP(SYS1,SYS2,...,T) plots the step response of several systems
SYS1,SYS2,... on a single plot. The time vector T is optional. You
can also specify a color, line style, and marker for each system, for
example:
step(sys1,'r',sys2,'y--',sys3,'gx').

[Y,T] = STEP(SYS) returns the output response Y and the time vector T
used for simulation. No plot is drawn on the screen. If SYS has NY
outputs and NU inputs, and LT = length(T), Y is an array of size
[LT NY NU] where Y(:,:,j) gives the step response of the j-th input
channel.

[Y,T,X] = STEP(SYS) also returns, for a state-space model SYS, the
state trajectory X, a LT-by-NX-by-NU array if SYS has NX states.

See STEPPLOT for additional graphical options for step response plots.

See also stepplot, impulse, initial, lsim, ltiview, DynamicSystem.
Overloaded methods:
DynamicSystem/step
uss/step
idmodel/step
idfrd/step
iddata/step
idnlmodel/step
Reference page in Help browser
doc control/step

追问

我用了最简答的语句 t=0:0.01:10; num=1;den=[1,2,1]; y=step(num,den,t);
但提示没有定义相应的函数，用help step确实能找到step的说明。这是咋回事呢？求教啊

追答

你输入的语句，在我的电脑上试了下可以运行（如下图）我装的matlab是7.11.0（R2020b）t=0:0.01:10; num=1;den=[1,2,1]; y=step(num,den,t);