Adding repetitive number to web address.

n=100;
for k=1:1:n
    B(k)=Locs(1,k)
    C(k)=Locs(2,k)
    r2(i)=webread('https:/........=B(i), C(i)');
end

In the above code I want to extract each value in Locs matrix and for each pair of value i.e., B and C I want to automatically calculate r2(i) which is basically calling a webside. When I code it like this to automatically use the values of B(i) and C(i) it gives me below mentioned error. But when I input values manually and calculate it works fine. I think there is an issue with the way I am giving B(i) and C(i) in the website. Please correct me.

Error using matlab.internal.webservices.HTTPConnector/copyContentToByteArray (line 373)

The server returned the status 400 with message "Bad Request" in response to the request to

URL https:.....

Error in readContentFromWebService (line 46)

byteArray = copyContentToByteArray(connection);

Error in webread (line 125)

[varargout{1:nargout}] = readContentFromWebService(connection, options);

Answer 1

[Walter Roberson]

    r2(k) = webread( "https:/........=" + B(k) + ", " + C(k));

assuming that the syntax is something followed by a literal equal sign, followed by the content of B(k), followed by a comma and then space, then the content of C(k)

Caution: it is uncommon for spaces to appear in URLs. When they do appear, they often have to be encoded as %20

[Muhammad Qaisar Fahim]

No its Like this

webread('https://abc.xyz.org/a1/mem21m?sites=30, -40')

It is actually an api to calculate some thing online where these 30 and 40 are the inputs which can be changed. I actually want to change these inputs 100 times automatically

[Walter Roberson]

What problem are you observing with the code I gave?

baseurl = "https://abc.xyz.org/a1/mem21m?sites="

baseurl = "https://abc.xyz.org/a1/mem21m?sites="

B = randi([-90 90], 1, 5)

B = 1×5

-38 -36 62 -83 -52

C = randi([-90 90], 1, 5)

C = 1×5

82 71 59 -30 -17

for k = 1 : length(B)
    thisurl = baseurl + B(k) + ", " + C(k)
end

thisurl = "https://abc.xyz.org/a1/mem21m?sites=-38, 82"

thisurl = "https://abc.xyz.org/a1/mem21m?sites=-36, 71"

thisurl = "https://abc.xyz.org/a1/mem21m?sites=62, 59"

thisurl = "https://abc.xyz.org/a1/mem21m?sites=-83, -30"

thisurl = "https://abc.xyz.org/a1/mem21m?sites=-52, -17"

... I still caution that you might need to use %20 instead of space.

[Muhammad Qaisar Fahim]

I am unable to understand one point here. Why you are writing it in double qoutataion and why are you not usingweb read? As the purpose of this web link is to calculate something from website not just populate the address

[Steven Lord]

Double quotes makes a string array as opposed to single quotes which makes a character array. The + operator for string arrays is concatenation; for character arrays it converts the characters to numeric codes and then performs addition.

S = "abc"

S = "abc"

C = 'abc'

C = 'abc'

S + 1 % "abc1"

ans = "abc1"

C + 1 % [98 99 100], the codes of the 'a', 'b', and 'c' characters plus 1

ans = 1×3

98 99 100

Walter didn't use webread because the point of the example was to show how to construct the addresses. You've already shown you are familiar with how to call webread, so what you needed assistance with was the text manipulation.

[Muhammad Qaisar Fahim]

Thanks yes this helps. Very nice explanation

[Walter Roberson]

baseurl = "https://abc.xyz.org/a1/mem21m?sites="

baseurl = "https://abc.xyz.org/a1/mem21m?sites="

B = randi([-90 90], 1, 5)

B = 1×5

85 84 -10 -89 13

C = randi([-90 90], 1, 5)

C = 1×5

-22 65 -9 -84 40

for k = 1 : length(B)
    thisurl = baseurl + B(k) + ", " + C(k)
    result{k} = webread(thisurl)
end

thisurl = "https://abc.xyz.org/a1/mem21m?sites=85, -22"

Error using webread
Could not access server. https://abc.xyz.org/a1/mem21m?sites=85,+-22.

And that is why I did not use webread(): I knew it would generate an error on the first attempt, so you would have seen only one example URL (because the error would have prevented the other example URL from being constructed.) As Steven indicates, the problem you were having trouble with was the text manipulation.