// Numbas version: exam_results_page_options {"name": "Basic R: Part 2a", "duration": 0, "metadata": {"description": "", "licence": "Creative Commons Attribution 4.0 International"}, "allQuestions": true, "shuffleQuestions": false, "percentPass": 0, "timing": {"allowPause": true, "timeout": {"action": "none", "message": ""}, "timedwarning": {"action": "none", "message": ""}}, "pickQuestions": 0, "navigation": {"onleave": {"action": "none", "message": ""}, "reverse": true, "allowregen": true, "showresultspage": "oncompletion", "preventleave": true, "browse": true, "showfrontpage": true}, "feedback": {"showtotalmark": true, "advicethreshold": 0, "allowrevealanswer": true, "feedbackmessages": [], "showactualmark": true, "showanswerstate": true, "intro": ""}, "type": "exam", "questions": [], "showQuestionGroupNames": false, "question_groups": [{"name": "", "pickingStrategy": "all-ordered", "pickQuestions": 0, "questions": [{"name": "Question 6 types of variables", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Christian Lawson-Perfect", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/7/"}, {"name": "Amy Chadwick", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/505/"}], "functions": {}, "ungrouped_variables": ["a", "type", "possible_values", "logical_values", "double_values", "dataframe_values", "character_values", "value"], "tags": [], "preamble": {"css": "", "js": ""}, "advice": "

A double is any number.
TRUE and FALSE are the only logical values.
Characters are surrounded by quotation marks. Note that \"5\" is a character, not a double!

", "rulesets": {}, "parts": [{"displayColumns": 0, "prompt": "

What type of variable is $x$?

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Character

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Logical

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Double

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Data frame

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> x = {value}

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Possible values for the given data type

"}, "value": {"definition": "random(possible_values)", "templateType": "anything", "group": "Ungrouped variables", "name": "value", "description": ""}, "character_values": {"definition": "['\"'+random([\"Fred\",\"x\"]+logical_values+double_values)+'\"']", "templateType": "anything", "group": "Ungrouped variables", "name": "character_values", "description": ""}, "double_values": {"definition": "repeat(random(1..10),3)+\nrepeat(random(-10..-1),3)", "templateType": "anything", "group": "Ungrouped variables", "name": "double_values", "description": ""}, "type": {"definition": "random([0,1,2])", "templateType": "anything", "group": "Ungrouped variables", "name": "type", "description": "

0 - character

1 - logical

2 - double

3 - data frame

"}}, "metadata": {"description": "", "licence": "Creative Commons Attribution 4.0 International"}, "type": "question", "showQuestionGroupNames": false, "question_groups": [{"name": "", "pickingStrategy": "all-ordered", "pickQuestions": 0, "questions": []}]}, {"name": "Question 10 length of vectors", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Christian Lawson-Perfect", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/7/"}, {"name": "Amy Chadwick", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/505/"}], "functions": {}, "ungrouped_variables": ["a", "c", "d"], "tags": [], "advice": "

a)

x is a vector holding the sequence of numbers between $\\var{a}$ and $\\var{a+c-1}$, inclusive, i.e. {join(list(a..a+c-1),', ')}.

length gives the number of elements in a vector. There are $\\var{c}$ elements in x.

x+{d} adds $\\var{d}$ to each element of x, so the resulting vector has the same length.

b)

y is a single number, so length(y) is $1$.

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What is the value of $y$?

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{c}

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{{c}+{a}+{d}}

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{{c}+{d}}

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{{a}+{d}}

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What is the value of $z$?

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{a}

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{c}

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{{c}+{d}}

> x = seq({a},{c+a-1})
> y = length(x+{d})
> z = length(y)

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x is a vector holding the sequence of numbers between $\\var{a}$ and $\\var{a+c-1}$, inclusive, i.e. {join(list(a..a+c-1),', ')}.

length(x) gives the number of elements in x. x has $\\var{c}$ elements.

", "rulesets": {}, "parts": [{"displayColumns": 0, "prompt": "

What is the value of $y$?

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{c+d}

", "

{{c}+{a}+{d}}

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{c}

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{{a}+{d}}

> x = seq({a},{c+a-1})
> y = length(x)+{d}

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x is a vector holding the sequence of numbers between $\\var{a}$ and $\\var{a+c-1}$, inclusive, i.e. {join(list(a..a+c-1),', ')}.

length(x) gives the number of elements in x. x has $\\var{c}$ elements.

$y = 1/\\operatorname{length}(x) = 1/\\var{c} = \\var{1/c}$

", "rulesets": {}, "parts": [{"displayColumns": 0, "prompt": "

What is the value of $y$?

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{1/c}

", "

{1/({c}+{a}+{d})}

", "

{{c}+{d}}

", "

{c}

> x = seq({a},{c+a-1})
> y = 1/(length(x))

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