i need help writing code in matlab that will plot data of 4 different variables onto one graph

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Neonmd 2021-7-23

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回答： Walter Roberson 2021-7-24

Help plotting data. When I do for loop nothing shows up on my plot figure.

I am given for example data like this: A b and c are just constants depending on the planets: T is the temp in celcius.

A B C

earth: 14.3145 2756.22 228.060

venus: 15.0717 3580.80 224.65

mars: 13.7819 2726.81 217.572

jupiter: 13.6608 2154.70 238.789

plot the 4 different planets datas on the same graph, plot the pressures from T=25C to T=125C with intervals of 1C

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dpb 2021-7-23

编辑：dpb 2021-7-23

See the examples for plot() in the documentation.

HINT: Do NOT use a loop; use an array (or at least vectors), "the MATLAB way"...if use the latter and not the former, then you'll need to use hold on, too.

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Answer 1

Walter Roberson 2021-7-24

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在 MATLAB Online 中打开

format long g

data = {

'earth', 14.3145, 2756.22, 228.060

'venus', 15.0717, 3580.80, 224.65

'mars', 13.7819, 2726.81, 217.572

'jupiter', 13.6608, 2154.70, 238.789

}

data = 4×4 cell array

{'earth' } {[14.3145]} {[2756.22]} {[ 228.06]} {'venus' } {[15.0717]} {[ 3580.8]} {[ 224.65]} {'mars' } {[13.7819]} {[2726.81]} {[217.572]} {'jupiter'} {[13.6608]} {[ 2154.7]} {[238.789]}

temperature = vertcat(data{:,4}) - 273.15;

variable2 = vertcat(data{:,2});

[temperature, idx] = sort(temperature);

variable2 = variable2(idx);

T = 25:125;

p = polyfit(temperature, variable2, length(temperature)-1);

interpolated2 = polyval(p, T);

plot(temperature, variable2, '*', T, interpolated2, 'b-')

hold on

for K = 1 : size(data,1)

text(temperature(K), variable2(K), data{K,1});

end

hold off

ylim([min(temperature)-50, max(interpolated2)+50])

This is an excellent case of "Garbage In, Garbage Out". You are asked to predict behaviour at temperatures that are 75C to 200C higher than you have any data for, and you have very limited amounts of data to predict from. The output probably has no meaningful relationship to the inputs.