Why is creating a handle for a bar graph delecting half of my plot?

I am trying to create a plot of number of rainy days each month for each of three cities. The first part of my code for this is:

    % code
>>f1=figure
>>xlab=['Jan';'Feb';'Mar';'Apr';'May';'Jun';'Jul';'Aug';'Sep';...
'Oct';'Nov';'Dec'];
>> bar(Month,[RainDaysP, RainDaysSS, RainDaysM])
>> set(gca,'XTickLabel',xlab)
>> axis([0 13 0 31])
>> ylabel('Number of rainy days','fontsize',16)
>> xlabel('Month','fontsize',16)
>> set(gca,'fontsize',16,'ticklength',[0.02,01])

Then I wanted to change the colour of each bar seperately, so I created a bar handle. My whole code is now:

    % code
>>f1=figure
>>xlab=['Jan';'Feb';'Mar';'Apr';'May';'Jun';'Jul';'Aug';'Sep';...
'Oct';'Nov';'Dec'];
>> bar(Month,[RainDaysP, RainDaysSS, RainDaysM])
>> set(gca,'XTickLabel',xlab)
>> axis([0 13 0 31])
>> ylabel('Number of rainy days','fontsize',16)
>> xlabel('Month','fontsize',16)
>> set(gca,'fontsize',16,'ticklength',[0.02,01])
>> p=bar(Month,[RainDaysP,RainDaysSS,RainDaysM])
>> set(p(1),'facecolor',[0 1 1])
>> set(p(2),'facecolor',[1 0 1])
>> set(p(3),'facecolor',[1 1 0])

My difficulty is that the first set of code produced a correct plot, however whenever I introduce the 'p=bar...' line I have been getting many problems. First the colours changed correctly, however the range of my y axis was now only up to 25 and not 31 as specified, and also I no longer had my x axis tick labels (showing the months), just numbers 1 to 12. Now, when I introduce the 'p=bar...' line, the only change that happens is that I lose half of my bar graph. The months now only show January through to July.

Any advice on where I am going wrong would be much appreciated. I have tried varying the code with 'hold on'/'hold off' to see if it makes a difference, but nothing has gotten me the graph I am looking for.

Answer 1

[Walter Roberson]

hold on

That is, the problem is that bar() is a high-level graphics operator that by default will erase whatever content you have in your current axis, as is the case for all high-level graphics operations. If you want to preserve the current content you need to use the hold call.

[Joanna Lada]

Thank you for your reply!

I am struggling with placing the hold on and hold off commonads correctly I think- maybe that is why it is not working. Could you point out where I am going wrong here? In the following code I have ditched changing the bar colours with the p handle just so I can get an idea of what I am doing with hold on and hold off, and it is still only producing January to July:

    % code
  f1=figure;
hold on
bar(Month,[RainDaysP,RainDaysSS,RainDaysM]);
axis([0 13 0 31])
ylabel('Number of rainy days','fontsize',16);
xlabel('Month','fontsize',16);
set(gca,'fontsize',16,'ticklength',[0.02,0]);
set(gca,'xticklabel',xlab);
hold off