I have the following function:
getcountof(x,l::ls) =
if x=l then (1 + getcountof(x,ls))
else getcountof(x,ls)
|getcountof(x,[]) = 0;
Can someone tell me whats wrong in it?
I get the error:
stdIn:1.2-1.17 Error: syntax error: deleting ELSE ID
stdIn:1.22-20.12 Error: syntax error: deleting RPAREN BAR ID
You've missed the fun keyword from the start of your definition!
Try this instead:
fun getcountof(x,l::ls) =
if x=l then (1 + getcountof(x,ls))
else getcountof(x,ls)
| getcountof(x,[]) = 0;
This is a trap for people familiar with Haskell.
Related
I'm dealing with a problem with the update function in Matlab.
conn=database('MySQL','user','password');)
selectquery_select = 'SELECT * FROM inputs WHERE i_read = 0';
data_select = select(conn,selectquery_select);
for j=1:size(data_select)
id_data = data_select(j,1);
id_data = string(id_data.(1));
time_data = data_select(j,4);
time_data = string(time_data.(1));
time_dataform = datetime(time_data,'InputFormat','yyyy-MM-dd HH:mm:ss');
y0=data_select(j,2);
y0 = str2num(string(y0.(1)));
r0=data_select(j,3);
r0 = str2num(string(r0.(1)));
if id_data == "115"
run("C:\Users\...\uu.m")
update(conn,'inputs','i_read',1,'WHERE (ID_code = "115") AND WHERE (i_Time = time_data)');
end
end
Basically, I'm taking some value from the database when i_read is equal to 0 (i_read is a boolean variable in the database that should give 1 if the value is already processed and 0 if not). After a value is read, we want to change the i_read in the database from 0 to 1. We decide to use the update function, but this gave us the following error:
Error using database.odbc.connection/update
Too many input arguments.
Error in Patient_Identification (line 57)
update(conn,'inputs','i_read',1,'WHERE (ID_code = "112") AND WHERE (i_Time = ', time_data,')');
Someone is able to help us with this problem? Thank you.
In simulink, I made some model using "MATLAB function"block
but I met error message here.
here is code and error message.
function [VTAS,postVTAS]=fcn(mode,initialVTAS,a,t,preVTAS)
if mode == 1
VTAS = initialVTAS + (a * t) ;
postVTAS = VTAS;
elseif mode == 2
datasize = length(preVTAS);
lastvalue = preVTAS(datasize);
VTAS = lastvalue + 0;
postVTAS = VTAS;
end
end
Output argument 'VTAS' is not assigned on some execution paths.
Function 'MATLAB Function' (#36.25.28), line 1, column 26:
"fcn"
Launch diagnostic report.
I think there is no problem about output "VTAS"
please teach me what is a problems.
As the compiler tells you, under some circumstances there is no output value assigned to VTAS. The reason is that you only assign values to that output if mode is 1 or 2. The compiler doesn't know what values are feasible for mode. To remedy this, you need to make sure that VTAS is assigned under any and all circumstances.
This could be accomplished by, e.g. adding an else construct, like so:
function [VTAS,postVTAS]=fcn(mode,initialVTAS,a,t,preVTAS)
if mode == 1
VTAS = initialVTAS + (a * t) ;
postVTAS = VTAS;
elseif mode == 2
datasize = length(preVTAS);
lastvalue = preVTAS(datasize);
VTAS = lastvalue + 0;
postVTAS = VTAS;
else
VTAS = NaN;
postVTAS = NaN;
end
end
Edit:
Additionally, it would be good practice for the else case to throw an error. This would be helpful for debugging.
As a minor note, for every case, postVTAS is equal to VTAS, so essentially it is superfluous to return both from the function.
I'm new to Matlab and now learning the basic grammar.
I've written the file GetBin.m:
function res = GetBin(num_bin, bin, val)
if val >= bin(num_bin - 1)
res = num_bin;
else
for i = (num_bin - 1) : 1
if val < bin(i)
res = i;
end
end
end
and I call it with:
num_bin = 5;
bin = [48.4,96.8,145.2,193.6]; % bin stands for the intermediate borders, so there are 5 bins
fea_val = GetBin(num_bin,bin,fea(1,1)) % fea is a pre-defined 280x4096 matrix
It returns error:
Error in GetBin (line 2)
if val >= bin(num_bin - 1)
Output argument "res" (and maybe others) not assigned during call to
"/Users/mac/Documents/MATLAB/GetBin.m>GetBin".
Could anybody tell me what's wrong here? Thanks.
You need to ensure that every possible path through your code assigns a value to res.
In your case, it looks like that's not the case, because you have a loop:
for i = (num_bins-1) : 1
...
end
That loop will never iterate (so it will never assign a value to res). You need to explicitly specify that it's a decrementing loop:
for i = (num_bins-1) : -1 : 1
...
end
For more info, see the documentation on the colon operator.
for i = (num_bin - 1) : -1 : 1
I am new in matlab I am trying to define a function and I keep getting this error
" input argument "ip" is undefined.
Error in ==> edge_mapping at 2
size_ip = size(ip(:,:,1)); "
here is my code
function[op1,op2,op3] = edge_mapping(ip)
size_ip = size(ip(:,:,1));
s=size_ip(1);
op1= cat(3,zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s));
op2= cat(3,zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s));
op3= cat(3,zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s),zeros(s));
for i = 1 : 10
op1(:,:,i)=edge(ip(:,:,i),'sobel');
op2(:,:,i)=edge(ip(:,:,i),'prewitt');
op3(:,:,i)=edge(ip(:,:,i),'canny');
end
function [op1, op2, op3] = edge_mapping(ip)
op1 = zeros(size(ip));
op2 = zeros(size(ip));
op3 = zeros(size(ip));
for i = 1 : size(ip, 3)
op1(:,:,i)=edge(ip(:,:,i),'sobel');
op2(:,:,i)=edge(ip(:,:,i),'prewitt');
op3(:,:,i)=edge(ip(:,:,i),'canny');
end
return
But I think it's better to write a simple function:
function op = edge_mapping(ip, edge_mode)
op = zeros(size(ip));
for i = 1 : size(ip, 3)
op(:,:,i)=edge(ip(:,:,i), edge_mode);
end
return
and then call it:
op_sobel = edge_mapping(ip, 'sobel');
op_prewitt = edge_mapping(ip, 'prewitt');
op_canny = edge_mapping(ip, 'canny');
This code is a function. It has to be save as m-file and run from MATLAB command line, script or another function as
[op1,op2,op3] = edge_mapping(ip);
where arguments ip, op1, op2, and op3 can have different names.
Make sure you have space after function keyword.
To avoid this error you can assign a default value for the input argument if it's undefined (not exist in the function's scope):
if ~exist(ip, 'var')
ip = []; %# or other default value
end
I try to test this in Scala Console (I mean console not script file):
while i < 10 {print(i) i += 1}
It doesn't work. I tried multiple lines it doesn't seem to either.
Am I obliged to use a script file just to test a simple loop ?
Yes it's possible. You have some syntax errors though:
var i = 0
while (i < 10) { println(i); i += 1 }
Or on multiple lines:
var i = 0
while (i < 10) {
println(i)
i += 1
}
As usual, there is more than one way to do this:
// join values beforehand and print the string in one go
println(0 to 9 mkString("\n"))
// using foreach
(0 to 9).foreach(println)
// using for
for(i <- 0 to 9) println(i)
scala> while i < 10 {print(i) i += 1}
<console>:1: error: '(' expected but identifier found.
while i < 10 {print(i) i += 1}
^
As indicated by the error message, a while must be followed by an "(", as the condition it tests for must be enclosed inside parenthesis. The same thing holds true for "if" and "for", by the way.
What you want is this:
var i = 0; while (i < 10) { print(i); i += 1 };
On the other hand, Scala encourages you to not use a mutable variable and while + condition
If you want to print the numbers from 0 to 9, use a sequence comprehension :
for (var <- range ) doSomethingWith (var)
In your case will be:
for (i <- 0 to 9) print (i)
(yes, the example looks pretty silly, but it helps to transition to a more "Scalaish" code)